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CATALOGUE
PRICE LIST
ENGINEERS' AND SURVEYORS'
INSTRUMENTS,
MADE BY
A. LIETZ & CO.
(Successors to Karl Rahsskopff,)
422 SACRAMENTO STREET,
SAN FRANCISCO, CAL.
*?
r»itioj:, ar, cuptthi.
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HE prices quoted in this list are as low as consistent
with first-class workmanship, and no deductions there-
from will be made. Customers ordering from a distance
will please remit by registered letter, money order, or draft,
made payable to us, or the goods will be sent C. O. D.
Parties in ordering goods, will please give the number
of article in this Catalogue.
Small articles can be sent by mail, at the purchaser's
risk, when the cost of postage, one cent for every ounce, is
remitted in addition to the price.
We furnish packing boxes at cost prices.
r 'Odstw survey,
.7. LIE I
vour note >une, asking me to
character as Mathematical Instru-
ment ma/.
For the six years since you succeeded to the business of
\ss1copff, I have been so well satisfied with the char-
of your workmanship upon the various kinds of Instru-
ments which I have intrust- <ur care that I have seen no
■i whatever to make any change.
Jn the matter of new instruments and novel devices you
have fully comprehended the wants of the observer and hair
intelligently supplied them.
Very respectfully,
GEORGE DAVIDSON.
San Francisco, May f4, 1888.
Messrs. .7. LIETZ & CO., San Francisco.
its: My acquaintance with your establishment for the
manufacture of Xauiical and Field Instruments, and the
knowledge I have of your excellent appliances for such work,
prompts me to a statement thereof, especially as you have
furnished me with a substantial proof of your workmanship
in the Transit purchased of you some months ago. This instru-
ment has since been constantly used in important surveys in an
extremely rough mountainous country, and I am informed by
my son who has been operating with it, that it is in every res-
pect exceedingly accurate in all operations for which a Tru
is designed. I am glad to express my satisfaction of its
results and consider it a high recommendation of your ability
Hi make superior instruments.
He spec! fully yours.
CALVIN BROWN, C. E.
Berkeley, Cab, May 24, (888.
,i. LIETZ & CO.. San Francisco, Cal.
Cattlemen: Having your Transit in use, I lake pleasure
in expressing my satisfaction. I am pleased particularly with
'he Tripod coupling, it saving much time.
Respectfully,
/,'. E. BUSH, Surveyor.
San Jose, Cat., June 4, 1888.
Messrs. A. LIETZ & CO., San Francisco.
Gentlemen: It is with great pleasure that we add our
testimony to the excellency of your Instruments. The two
Transits and one large Y Level bought of you, are in every
respect as good and serviceable as the instruments made by the
most reputed of eastern firms, and as a purely California or
home production deserve the greatest credit.
The graduations made. on your own graduating machine,
are clear,, sharp and exact, the glasses of the very best make
and power, and the needles much superior to the general run
of needles.
Your Tripod coupling is at once simple, effective and safe,
and we consider it better than any other coupling used by
other maters.
We can but congratulate you upon your success in the
production of A No. 1 California made instrument and heartily
recommend you to the profession.
Very truly yours,
HERMANN BROS.,
Surveyors and C. E.
La Porte, Cat, June 5, 1888.
Messrs. LIETZ & CO., San Francisco.
Gentlemen: I take pleasure in stating that the Mountain
Transit with which: you have provided me in April, 1887, has
proved excellent. In regard to accuracy of the .graduation,
stability of Tripod, reliability of instrument in its adjustments
and strength combined with lightness, it gives entire satisfaction.
Very respectfully,
WM. SCHVLD, C. E.,
V. S. Deputy Mineral Land Surveyor.
Oroville, Cat., September
■ 12, 1887.
Messrs.
A. LIETZ & CO.
Sirs: The Leveling Rod sent me is entirely satisfactory,
in fact I like it better than any Rod I have had occasion to use.
Very truly yours,
0.
M. EN SLOW.
CATALOGUE
PRICE LIST
ENGINEERS' AND SURVEYORS'
INSTRUMENTS,
MADE BY
A. LIETZ & CO
(Successors to Karl Rahsskopff,)
-422 SACRAMENTO STREET,
SAN FRANCISCO, CAL.
.PRICE, 2 5 CENTS.
SAN FEANCISCO:
JOS. WINTERBURN & CO., Primers and Electrotypers, 417 Clay Street.
Between Sansome and Battery Streets,
1888.
PREFACE.
(0)\ ft/E herewith present to the Engineering Profession our new
"" y Catalogue, giving a detailed description of our instruments
and some information which may be of service to the reader.
The various improvements we have added to our instruments lately
have led us to issue this publication. Our Coupling — a new method of
rapidly and conveniently attaching or detaching the instrument to or
from its tripod — is of great importance, and, undoubtedly, the most
valuable improvement made during recent years in Surveying Instru-
ments. Of almost equal value is our improved Telescope, having
nearly double the power of ordinary ones. Our new Tangent Screw
and Clamp; reduction in the weight of instruments with an increase of
strength; their construction in such a -manner as to bring the center of
gravity nearer to the tripod head than any other make of instruments,
thus making them more stable; the employment of composition and bell
metal instead of common brass, and several minor improvements, have
all contributed to the value of our instruments, and will, we trust, be
appreciated by the profession.
We shall leave it to the intelligent reader to decide as to the
superiority of our instruments over others. We shall only call attention
to the different merits and points of ours, and invite comparison.
For the convenience of our customers, we will furnish any articles
not on our list, but described in the catalogue of any American manu-
facturer or dealer in mathematical or optical instruments, at catalogue
prices.
3l. LIETZ & CO,
PART I.
NEW TRIPOD COUPLING.
This important improvement, which solves a problem that bus occupied the
attention of Instrument Makers and Engineers for years, and which has met the
approbation of all who hid occasion to either use or see it, was invented by us dur-
ing the past year. Before describing it, we will mention the different methods of
connecting the instrument to the tripod that have been employed, so far, and the
defects they are all more or less possessed of.
There are known in general surveying two kinds of Transits, the Engineers' and
the Surveyors'. The Engineers' Transit, as now made by almost every maker, is
attached to the tripod by means of a screw at the base plate, and cannot be taken apart
above the leveling screws. The Surveyors' Transit is attachable and detachable in
the centre above the leveling screws. In most cases the parallel screws can also
be detached from the tripod in the same manner as the Engineers' Transit, but in a
great many they remain with the tripod.
To attach an Engineers' Transit by means of the screw at the base, is a very
tedious aud unsafe method, as probably most every engineer knows. Very often the
screw will not catch, thus making the instrument liable to tip over. Besides, since
its whole weight while turning rests on the screw, it naturally wears out the thread
very soon.
The mode of attaching the Surveyors' Transit in the center is, though more
safe, very defective. It is almost impossible to keep the center clean; a little dirt
will often cause it to move very hard, and sometimes it commences to fret. But the
greatest fault is its necessitating the construction of what is called "the flat center"
for turning the upper plate. Iu such an instrument the plates stand too high above
the leveling screws, and therefore cause unsteadiness. We believe it to be very diffi-
cult, if not impossible, to do accurate work with such an instrument, and will explain
it more fully in our description of Transits.
The same reason which led to taking apart the Transit above the leveling screws,
viz. : "The unsafety and inconvenience of attaching and detaching," also caused the
different methods of taking apart levels. While some are constructed so as to leave
the center on the instrument proper, others allow it to remain in the parallel plate,
"We believe the latter method the most defective of the two, because it throws the Y's
out of adjustment every time the least dirt settles on either the socket or thecone, and
because the bar and Y's have to be brought too high above the leveling screws.
Both constructions have oue common defect. The cone and the socket have to be
stuck together tight to make the instrument steady, and in order to take it off again,
it generally requires a sudden shock, which, of course, is liable to throw out the
adjustment.
The foregoing description has shown the defects which all instruments are pos-
sessed of. We shall now describe our new arrangement, which remedies them.
On the tripod head, instead of the ordinary screw, we have three claws, (,as
shown in the accompanying cut) the base plate of the instrument is swallow-tail
shaped on the inside (as shown by F) and is provided with the spring case C. The
connection of the two is done by letting one of the cuts on the base plate meet either
one of the claws on the tripod head, when a third of a revolution to the right will
make the connection, the same time the spring C will fall into a hole on the tripod
head, and thus prevent a disconnection, the latter can be done by lifting the
spring C and turning to the left. If the tripod head should have been worn or bent
by accident, the movable claw D, which is worked by the side screw E (with the
large adjusting pin) will still enable to give the coupling friction enough to hold the
instrument perfectly firm on the tripod.
CATALOGUE AND PKICE LIST OF
Li
GK
The chief merit of our arrangement is, that it enables us to attach or detach
the instrument to or from its tripod more rapidly, firmly and safely than any other
device so far known, and without dividing the instrument into two parts, which lat-
ter method is always injurious to its accuracy, stability, etc. In moving from one
station to another the' engineer can take the instrument and leave the tripod to be
carried by his assistant. To this we might add that it is more durable, easier to
keep clean and cannot get out of repair.
TRANSITS.
The unreliability of the flat center or Surveyors' Transit has, during recent
years, caused its being discarded by almost all Engineers and by a great many
Surveyors. This is proved by the fact, that the very firm which introduced this stj'le
about 50 years ago, has. according to their own statement, almost abandoned it, and
adopted for most of their instruments the long compound center construction. The
greater friction of the plates upon each other in a flat center instrument, is liable to
move the limb slightly, when the upper plate is turned in order to take an angle, and
therefore will not give the correct one. Different readings taken for one angle, will
often give different results, as probably all those who have used this style will have
observed. One of the results of this great friction, is its wearing out the centers
rapidly. Another defeat of the flat center Transit, is its unsteadiness, which in a
windy day is often so great as to render useless the attachments of a level to the
telescope. One error which can be found frequently in these instruments, is the
eccentricity of the limb, caused by an inaccurate centering on the graduating engine.
A. LIETZ A CO. 5
As the l o w er plate or limb is al Hie noe time the center, it is evident thai rooh nu
iu not be remedied, anli Ination is taken "IT, and a new one put on.
-inly advantage which is claimed by the few advocates of the flat center, is
its ability to withal This is, however, <-i little importance, con-
aidering thai a fall <>r blow which is capable of injuring long compound centers will
in nine cases out of ten also bend the plates, standards, axis, &c, and necessitate its
patent instrument maker.
From the above it will easily be Been, that a tint center instrument is imperfect,
and cau not . lion; we will therefore state here, that we do not and will
not manufacture this style. The superior qualities of the long compound center
instrument will more than make up for the small additional cost, and we advise pur-
chasers, wishing to save money, to rather buy a second-hand long compound center
than a new flat center Transit.
We shall now describe those parts of our Transits, which are common to several
or all of our different styles.
THE CENTERS.
The length of our centres is from 2% to 4 inches, according to size and style of
instrument. To the best of our belief this is more than is possessed by the. instru-
ments of any of the many different makers, which are constantly passing through
our hands for repairing. Yet, by examining our cuts, it will be noticed that the limb
and vernier plates are nearer to the tripod head than theirs, owing to the judicious
placing of the centers, which reach almost down to the base, thus insuring the utmost
stability. Alt&gether regarding steadiness of construction the reader will cousult
his best interests by comparing our cuts with those of other makers, which wi.l
guide him in forming a correct idea better than the arguments of either ourselves or
others based ou mere assertion.
SHIFTING PLATEN.
All our Transits are furnished with shifting plates for the precise centering of
the instrument over a point after it is set approximately by the legs. This is of great
convenience to the engineer, and, indeed we have made the observation, that whoever
had occasion to use it once, will be unwilling to dispense with it afterwards. In
order to centre the instrument, two of the leveling screws have to be loosened, then
Bhift the instrument until the plumb bob is over the point aud level up, which will
clamp it again. We have placed a thin metal plate under the leveling screws, pre-
venting the accumulation of dirt between the two shifting plates.
LEVELING S(KFUS.
As the leveling screws are used more than any other part of the instrument, it is
evident that they should be very durable. Ours have a very deep thread rounded a
little on the edge, which insures a nice smooth motion and a greater durability than
sharp-edged threads. The screws are made of composition metal. We do not use
the common round nut for the leveling screws to work in, but have the lower part of
all our instruments so constructed as to allow the leveling screws to pass through a
slotted star, A, Fig. B. on Page 4, any lost motion of the screw can be taken up by
the clamp screw B. This is of great importance ou Leveling Instruments or Tran-
sits used for leveling. By placing caps above the screws, these are well protected
against dirt.
TRIPOD LEGS.
We have adopted the new style of fitting legs to the tripod head, as the engraving
will show. Instead of fitting the leg between two brass cheeks, we fit one cheek in
the leg. In the old construction, the cheeks, when drawn closer by the bolts in order
to tighten the leg when this gets Loose, will often spring the plate or loosen the screws
which hold the latter. In the new arrangement the tightening of the legs will not
effect the plate in the least. While by the old method the legs would only fit at the
lower part of cheeks when drawn in by the bolts, they will in the new one always fit
the whole surface of the cheek, and will, after ten years' use, be just as steady as
when new. The shoes are made tapering gradually to a sharp point and securely
fastened to the leg.
If ordered, we furnish the round legs instead of the split ones.
b CATALOGUE AND PRICE LIST OE
SPIRIT LEVELS.
All Spirit Levels are ground to a proper curve and tested by us in person. Our
advice is, not to meddle too frequently with the adjustment of a spirit level. Though
it may appear to be out one day, it may be in perfect adjustment other days. It is
the function of a Spirit Level to indicate the changes taking place in an instrument,
so that the engineer may make proper allowance and apply his corrections, as the
character of his work may require. The finer the instrument, the more sensitive the
spirit levels must be, in order to admit of corrections to arrive at closer results. As
a rule, a spirit level that does not indicate changes taking place in an instrument, is
too insensitive for the character of the instrument, and in many cases entirely unfit
or reasonable good work.
GRADUATION.
This very important part of a good instrument we guarantee exact and accurately
centered, opposite verniers reading the same. The lines are straight, thoroughly
black and uniform in width. There are two double verniers in every transit to read
angles with great rapidity as well as to make four separate readings at every sight,
■when extreme accuracy in the repetition of angles is required. The horizontal circle
is graduated from J to 360° with two sets of figures, running in opposite directions
(unless ordered differently). The figures are large and distinct, and, to avoid mis-
takes in reading, the figures of these two sets of graduations, and those on the ver-
niers, are inclined in opposite directions, thus indicating the directions in which the
verniers should be read.
The remark is hardly necessary, that an instrument should always have two
verniers, for the reason that the manufacturer himself cannot, without losing a great
deal of time, be sure whether the graduation is correct or not, even if it is done on
the most perfect engine. We believe that the facility of proving graduation and
centers, which can be done only by having two opposite verniers, will be fully worth
the slight additional cost. "We will here venture the assertion, that those instruments
■with one vernier and fiat center, generally known as surveyors' transits, are made in
a manner not admitting of accuracy. To distinguish the verniers one from another
we engrave the letter A on one, and B on the other, which is very convenient for
those who always read only one vernier, as well as for those who read both.
It is well understood that the graduation is the most important point in a Transit,
and any error renders the instrument almost useless, even if all the other parts are
perfect. The most accurate graduation will, however, be of no value without a well
fitting center. To prove both, several methods are employed. The surest test is to
clamp the vernier plate to any point of the circle, and if by adding the two vernier
readings together the sum is =180, and this same proceeding is repeated a number
of times all around the circle with the same result) then they are correct. The grad-
uation of au instrument having but one vernier can only be tested with the telescope,
■which test would take several days' time. All instruments, unless ordered differ-
ently, have the verniers so placed that they may be read without changing the
position of the engineer after sighting through the telescope.
Glass covers protect the arc and verniers from exposure. For ease in reading
the verniers, we have added to all of our instruments two plates of white glass, which
cast a very clear light on the verniers in any position.
To graduate on solid silver adds $10 to the first outlay for the instrument, but
its many advantages, great permanency and smoothness of surface renders it the
only satisfactory surface for fine graduations.
THE COMPASS.
Our needles differ somewhat from others in shape, being a little lighter in the
centre than towards the ends, for the reason that the magnetism is always in the
ends only, decreasing towards the centre, so that all the metal there may bs called
dead weight. Compared with those of other makers, our needles are also a little
lighter, which conditions the increased durability of the point.
Hard steel has the capacity of retaining magnetism longer and better than when
tempered, and we therefore now leave one-half inch on both ends perfectly hard.
The closest attention is given to the pin and centre cap, on which the accuracy or
sensitiveness of the needle principally depends.
A. LIETZ * CO. (
The Lifter arrangement is made in snob, a manner us to raise and lower the needle
..•lit the sodden jerking and (ailing, which so often is the cause for
muj! out of the point and .run
(.it tmi vn it SCREW.
This attachment was first introduced by Prof. Stampfer, of the Vienna Polyteoh-
lt does not add to the weight of the inatrtunent, and once used we have
found it to be universally approved by our customers. By means of it grad s can be
can be
with great rapidity. Indeed this attachment to an engineer's transit is one
useful introductions in practical engineering. It is so universal in its
application to railroad and general work, that when ouce. used it will afterwards form
an indispensable pari of a outfit,
CEAMP AXB TANGENT SCREWS.
The low.r damp screw of our transits are of the best devised plan, they are
strong and rigid and answer the slightest touch.
The upper clamp is so constructed that it leaves the limb circle untouched, just
grasping the sleeve of outside center against this clamp works a fine micrometer
with opposing spring. This clamp answers the slightest touch and is very
rigid and the micrometer screw can never have any lost motion, as the opposing
spring takes up all possible wear.
In closing these remark?, we shall call the attention of the reader to the loss of
time and annoyance arising from a Tangent Screw having "lost motion" while ad-
justing the line of eollimation in the telescope. While revolving this, the plate is
liable to turn slightly, and the operator is never sure whether the cross hairs are ia
adjustment or not.
FIXED STADIA WIRES FOR DISTANCE
MEASUREMENT.
We have specially devised an optical and mechanical apparatus for the purpose
of placing fixed, or non-adjustable stadia wires so accurately upon the diaphragms
of -our telescopes that their distance apart will read I s : 10(> v t on any leveling rod,
as with the gradienter screw, thus dispensing with a special rod.
It is well known that adjustable stadia wires are so apt to change their distance
apart with every change of temperature, that no reliance can be placed upon them
unless previously adjusted, With fixed stadia wires, annoyances of this kind are
obviated — they are reliable at all Hairs.
As regards the degree of accuracy attainable by the use of fixed stadia wires,
experiments with our powerful telescopes, made optically as perfect as the most
advanced optical and mechanical skill enable, us, warrant us in sa}'ing that with some
experience and proper care the results obtained will approximate and even equal
those obtained by chain measurements. The price for this accessory in any new
instrument is only $3.00, but if inserted into a telescope sent to us forthat purpose,
we must charge $10.00. We advise to order both the gradieuter screw and the
fixed stadia wires, as each in itself, separately or jointly, will prove of great value.
GENERAL MATTERS.
The general demand in these days is for light instruments. We have succeeded
in producing such, without reducing their strength, but rather adding to it. This is
accomplished by the method of bracing and ribbing all the heavy parts. By removing
metal in such places which did not impart strength, and applying a part of it to
points where the most strength is required, we have obtained stronger and
somewhat lighter instruments.
Yellow brass has been entirely discarded by us, composition and bell metal being
employed exclusively. The greater strength these metals have, compared with the
former, is an important item, especially in case of accidents. When such take place
with a yellow brass Transit instrument, the limb in most instances will have to be
redivided, while when made of hard metal, it must be a very severe blow or fall
which is capable of bending it, so as to require a new graduation. Many an accident
8 CATALOGUE AND PRICE LIST OF
which will damage a yellow brass instrument sufficiently to necessitate its being re-
paired, will not effect one made of hard metal. We ought to say here, that the em-
ployment of the harder metals increases the cost of manufacture, and this is the sole
reason why it is not adopted by every maker.
Another defect yellow brass is possessed of is, that it easily frets! To prevent
this as much as possible, we use for every movement two different metals, for one
part composition, and for the other bell metal. Thus the axis to telescope is made
of composition metal, the centre to the vernier plate of bell metal, that to the Iinub
of composition, and the leveling screw, again of bell metal. The collars of the
Level telescopes are made of ex':v& hard bell metal, cast especially for us, to prevent
wear.
LEGS.
These are made of well-seasoned ash. Experience has shown us that ash is
preferable to mahogany. In fact for legs, the latter is even inferior to black walnut,
for the reason, that if exposed to the weather and dampness of the ground, this soon
becomes rotten, an observation which almost every engineer has made. Many in-
stances as known to us where legs, after an ordinary use of two or three years,
broke right above the shoe. For legs, we believe ash the best, being very durable
and standing firmer than mahogany does.
The thickness of the wood of the boxes is % of an inch; they are nicely finished
and provided with lock, key, brass hooks and leather strap for carrying conveniently.
PACKING OF INSTRUMENTS.
Every possible precaution is taken by us to secure safety. Each box is pro-
vided with adjusting pins and sun shade, a plumb bob, and magnifier for reading the
graduation, is also furnished with Transits.
CARE OF INSTRUMENTS.
The usefulness of an instrument can be preserved for many years if proper care
is taken of the same. We shall therefore mention a few of the principal points which
the engineer will do well to observe.
To preserve the sensitiveness of the needle, the dulling of the centre pin must be
avoided. The instrument should never be lifted without being sure the needle is up,
and, if by letting it down again the swing is too large, it should be gently stopped
when within a few decrees of its natural bearing. Should the point become dull, it is
best to have it fixed by an instrument-maker; if such, however, is not accessible, or no
time can be spared, a watchmaker perhaps can do it. It must be remembered, how-
ever, that after being sharpened the point must be centered, that is, must be brought
in the center of the graduation. This work, however, can only be relied upon if done
by the instrument-maker.
If a needle is made of good steel, well hardened and properly chargpd, it will not
often Jose its magnetism, and if, when placed away, it is always brought to lie in the
meridian, it will retain, or even increase its polarity. It should not be left resting on
the point, but after it has assumed its position it should be raised against the glass. If
a needle has lost its magnetism it can be charged again with an ordinary horse sboe
magnet; one of three inches in length will be suitable for this purpose. The opera-
tion is this: hold the magnet with the poles upward, then, with a gentle pressure, pass
each pole of the needle from center to extremity over the opposite pole of the magnet,
describing, before each pass, a circle with a diameter of aboixt double the length of the
needle, taking care not to return it in a path near the pole. If the magnet is strong
enough, the needle need not be taken out at all, but by raising it against the glass and
then passing the magnet over this, it will be charged sufficiently. After charging , the
needle has lost its balance, which can easily be restored by shifting the brass wire on
the South end.
The general tendency in the use of screws is to overstrain them. This should
never be done, especially with the cross-wire screws, which, when too much tightened,
are liable to constant change and loss of adjustment. Leveling and clamp screws also
A LIETZ A 00. l J
nhoui-' ' Bthem "'it boodi r and sometimes causes fretting.
If tin- thej should be taken oul and brushed with either soap and water or
ne. Tin- nutscan best be cleaned by screwing a fiat piece of soft wood through
(hair apertures. In patting together, grease them slightly.
Fretting of the centers and of the telescope- si ids will Interfere more with ac< i
w irking of the instrument than any other part out of order. They Bhonld be watched
then ! Bely, him) its soon as any rough motion manifests itself, it should be
it possible, by an instrument-maker. If this cannot be hud, and the
fretting is in the Blide, firsl scrape and then burnish down the place where it frets. It
mm be Round slightly with * >i I and very fine pumice stone dust, which is best
obtained by rubbing two pieces on each other. After grinding them a little, the tubes
shonl . : ind placed together again, with oil only, then move them in and out
u number of times, wipe the oil off and finally put them together when dry. If the
fretting takes place in the centers (when properly made and constructed, so that they
do not come apart in detaching the instrument from the tripod, this will never happen >.
employ the same mentis, and if this is uot effective, place a washer, made of paper or
a thin card, between the shoulders. This will cause a shake, making accuracy impos-
sible, and produce errors of parallax in reading off, which, however, is better than
destroying the centers wholly. The best grease for centers is very fine watch oil. Iu
regard to our centers, we can say that no fretting will ever happen, as they are always
red and carefully made The object slide should not be greased. Never ush
emery piper or emery in repairing any movement, as it can not be removed again and
will grind continually. For greasing, leveling and clamp screws, pinions, etc., good
rendered marrow should be used.
In cleaning object and eye piece glasses, use a soft rag or chamois leather. If
the glasses should become greasy or very dirty, wash them with alcohol. The inside
of the glasses will very seldom require cleaning, and it is advisable not to take the
telescope apart often, as it destroys adjustment, especially in those instruments in
which the object glasses are loose iu the cell. If dust should settle on the cross hairs,
it is best not to touch them. The only means which may be tripd is by taking out
the object glass and eye piece and blowing gently through the tube. For dusting off
an instrument a camel's hair brush is best suited. It will brush dust better out of
the corners than can be done with a rag, aud preserves the lacquer. Its use is espec-
ially recommended for cleaning limb, vernier aud compass ring.
It is advisable to look sometimes after the fitting of legs and shoes. If there is
any shake in the legs, or any shoe loose, the instrument can not be steady.
There should be no delay in repairing defects.
If an instrument is upset, beuding centers aud plates, do not turn it unnecessarily,
as it will spoil the graduation, but send it to a competent instrument-maker immedi-
ately.
ADJUSTMENTS.
All the various adjustments which the engineer is required to look over occasional-
ly consist in placing certain points, either at right angles or parallel with others. To
adjust the verniers and compass, consists in placing certain points iu a straight line,
but as these adjustments are always made by the instrument-maker, they should
hardly be termed such. We have inserted that of the needle and point, as these
sometimes get out of order and are easy to correct. The adjustment of verniers and
limb, if properly done, will not get out of order from ordinary use.
The general method used in performing the various adjustments is that of rever-
sions. As these always double any existing error, it is evident that the mean between
the difference indicates the true point. "We shall commence by giving the adjustments
to transits, which, in practice, should be made in the same order as given here.
OF TRANSITS.
I. I.KVKIX
The object of this adjustment is to briug the levels at right angles to the centers
of the instrument, so that when the bubbles are brought in the center of the tube, the
vertical axis of the instrument stands in a true vertical position.
10 CATALOGUE AND PRICE LIST OF
To perform it, bring the bubble in the center of the tube by means of the leveling
screws, then turn the instrument 180 degrees. Shoiild the bubbles not stand in the
centers of the tubes again, correct one-half the difference by means of the capstan
head screws of the levels, the other half with the leveling screws. If the proper cor-
rections have been applied, the bubbles will remain in the center in any position of the
instrument; if not, the same operation must be repeated. If the levels should be
out much, it is best to adjust one, approximately, and then the other.
II. THE STANDARD BEARINGS.
The adjustment of these is necessary in order to make the telescope revolve in a
true vertical plane when the centers of the instrument stand in a vertical position. To
perform it, set up the instrument about fifty feet distant from a house. Take a well-
defined point as high as possible, then turn the telescope and take another as low as
can be obtained. After this, reverse the instrument on its center and direct the tel-
escope again to one of the observed points. If, by turning, it does not strike the other
point, correct one-half the difference, and the adjustment is done. It is not necessary
to level the instrument, but preferable to bring it in such a position which permits to
take two well-defined points. Care should, however, be taken that the observation
is made at the intersection of the cross-wires, and that the instrument is securely
clamped.
This adjustment should always be made before that of the cross-wires, for the
reason that, unless points of equal height are taken for the latter, the adjustment will
not be correct, if the axis does not revolve in a vertical plane. We make this remark
because some catalogues are evidently in error on this point.
III. THE CROSS-WIRES.
The object of this adjustment is to make the line of collimation perpendicular to
the axis, upon which the telescope revolves.
We assume that the telescope stands in the center of the instrument, that the
tubes are perfectly straight, and are set at right angles with the axis upon which the
telescope revolves, points which must be accurately performed by the instrument
maker, and which are necessary, if the adjustment on a long distance shall also be
correct on a short one.
There are two methods employed. The first one, which is most generally used,
consists in taking back and fore-sights. Before making the adjustment, the vertical
wire must be set truly vertical, so that the upper and lower end will remain upon the
object if the telescope is depressed or raised. In order to do this, the instrument
must be first leveled up.
Having performed this, proceed in the following manner: clamp the instrument,
and by means of the taugeut screw, set the intersection of the wires on some well
defined point from one to five hundred feet distant, then revolve the telescope and take
or place an object in the opposite directions at about the same distance. Now
nnclamp the instrument, turn it half way round, clamp it again, and set the wires again
on the first point. If then, by revolving the telescope, the intersection bisects the
second object, the vertical wire is in adjustment, If such is not the case, correct with
the two capstan head screws, on the sides of the telescope, by moving the vertical wire
back one quarter of the space between the point now obtained and the second
object. If the correction has been exactly one quarter, the wire will be adjusted,
if not, the same proceeding must be repeated. The reason why the correction is only
one fourth is evident from the fact, that in first revolving the telescope, the error is
doubled; then in revolving it again after the instrument has been reversed, the error
is again doubled, but on the opposite side.
It is not necessary to level the instrument while making this adjustment, but in
case leveling is dispensed with, the observation must always be made at the intersec-
tion of the wires. It must be remembered that the image at the cross-wires is inverted,
that, consequently, the screws must be moved in apparently wrong directions. Old
instruments which have back lash in the tangent screw, should be turned very carefully
so as not to change their position.
The second method consists in locating with the telescope three points in one di-
rection, which are necessarily in a straight line, no matter how much the wires are out
of adjustment. The instrument is then moved to the center point and the wire set on
either of the two other points. Then revolve the telescope and see whether the wire
A. LIETZ * CO. 11
the wire is in adjustment; if not, correotby mov-
ing it midway between tli<- poinl obtained ami the trne point. This method requires
the instrument.
We h only of the vertical wire, as this is the most impor-
tant in ■ Ti in a plum Transit that is. one without Level to teles-
ami without vertical circle the horizontal wire simpbj serves to define the o<
of the vertical wire, so that no trior may arise in case the latter does not stand in a
vertical direction.
If B level is attached to the telescope, the horizontal hair shonldbe brought ill the
optic the level is s«-t parallel with the line of eollimatiou; otherwise,
if adjusted for long distances, it will not be correct for short ones.
To perform adjustments, set up the instrument alongside a house or fence and
level up carefully. Then damp the telescope and by means of the tangent screw take
a point several hundred feel distant; then turn the instrument on its center, and mark
a point on the house or fence about 10 feet distant. Now unclamp the telescope, re-
verse it, clamp it again and set the wire again on the nearest point. Then turn the
instrument on the center and see whether the wire bisects the other point. If not,
correct by moving the wire half way between the two.
No directions are given for this adjustment in the catalogue of any other maker,
which omission has for its cause their assumption that no accurate leveling can be
done with a Transit; a supposition which we do not share with them.
IV. THE LEVEL TO TELESCOPE.
The object of this adjustment is to make the level parallel with the line of eolli-
matiou. The method by which this is accomplished is based on the priuciple that
points taken with the same angle of elevation or depression, and equally distant from
the instrument, are of equal height.
To perform adjustment, the instrument must be carefully leveled, and on opposite
sides, at equal distances, stakes must be driven, giving an equal reading. These two
points are necessarily on a level with each other. Now move the instrument to a
point in a line with both and about 10 ftet distant from one. Level again; take a
reading on the nearest, and then another on the further stake. If both agree, the
level is in adjustment; if not, move the wire with the tangent screw over nearly the
whole error, and sight again at the nearest stake. Repeat this until the readings are
the same on both, when the telescope is truly horizontal. Now bring the bubble in
the center of the tube, and the adjustment is completed.
THE ZERO MM. OF THE VERTICAL CIRCLE.
This adjustment, when once made by the instrument maker, will seldom get out
of order. The object is to make the zero liues of the vernier circle agree when the
level of the telescope is truly horizontal and the centers of the instrument stand in a
true vertical position.
To perform adjustment, the instrument must be carefully leveled; first, with the
small levels on the plates, and then with the level to telescope. "When this has been
done, shift the vernier until the zero lines cut each other.
OF THE Y LEVEL,
This requires three adjustments, viz.: 1. Making the level parallel with the
bottoms of the collars. 2. Adjusting the Y's so that the bubble will be at a right
angle to the vertical axis of the instrument. 3. Adjusting the line of collimation.
THE LEVEL.
The object of this adjustment is to make the level parallel with the line of col-
limation. At the same time the axis of the level must be brought in a plane with
that of the telescope.
It is best first to bring the level and telescope into a vertical plane: i, e., to cor-
rect the side motion of the level, which Is done in the following manner: Clamp the
instrument and bring the level in the centre of the tube; then turn the telescope in
the Y's so as to bring the level on either side of the bar. If the bubble changes its
12 CATALOGUE AND PRICE LIST OF
position, it shows thfit its axis is not in a plane with that of the telescope. Correct
by moving the two side screws until the bubble is half way back. If the level is
funnel-shaped, which is often the case in poorly made instruments, the adjustment
cannot be properly done, and the operator must always take care to have the level
stand over the center of the bar.
The level must now be made parallel with the bottom of the collars, which is
done in this manner: bring the bubble in the centre of the tube, then carefully
reverse the telescope in the Y's, end for end. The motion of the bubble is the
double error, which is removed by bringing this half way back by means of the
adjusting nuts, the other half is. corrected with the leveling screws. Repeat the
same operation until the bubble remains in the centre.
Remarks. — To make the level parallel with the line of collimation it is only pos-
sible if the collars are of equal diameter. If such is not the case, the instrument
will not beany better than a Dumpy Level, and must be adjusted as such. The level
can be made exactly parallel to the bottom of the collars; the Y's adjusted so that
the bubble remains in the center of the tube; the line of collimation brought in the
centre of the revolution of the telescope, this reversed end for end in the Y's, leav-
ing the bubble in the centre, no matter how much difference there may be in the
diameter of the collars. It is the general opinion among engineers that after level,
Y's and cross-wires are adjusted, the instrument must be correct, while this is by no
means certain, as the least difference in the size of the collars, which difference is
sometimes found in new instruments, more often produced by unequal wear, denting
etc., will throw out the line of collimation considerably. It is therefore advisable
that the equality of the collars should be tested from time to time, which can only
be done by taking a tost level. If found incorrect, it can only be remedied by the
instrument-maker. More information regarding this point can be found under
"Telescopes," where the subject has been treated more in detail.
THE Y'S
The object of this adjustment is to place the level and the line of collimation at
right angles to the centre .
To perform it bring the bubble in the centre of the tube and over two opposite
leveling screws, then turn the instrument half way around on its centre. The
difference in the position of the bubble is the double error, one half of which is cor-
rected with the nuts, and the other half with the leveling screws.
THE CROSS WIRES.
The object is to place the cross web or line of collimation in the optical axis of
the telescope, so that their intersection will remain on an object in revolving the
telescope.
To perform adjustment, set the intersection of the wires on some point about
two hundred feet distant, then revolve the telescope half way around. If the wires
have moved away from the point, bring them half way back.
Remarks. — In this, as well as in any other telescope, we assume that the tubes
are straight, the object glass well centered, and the slide well fitted. If such is not
the case, the telescope can only be adjusted for certain distances, It is urged by
some makers that it is almost impossible to produce straight tubes, and that, there-
fore, the object slide must be adjustable. This is, however, not so. Perfectly straight
tubes can be made if only the necessary time and money is expended. The fact is,
that in most of these instrumen s the object glass is not centered, the slide poorly
fitted, etc., which is by far more injurious than ever if the tubes are not quite
straight; besides, the constant working of the slide in the adjustable ring will loosen
the screws and cause a great deal of annoyance.
OF THE SURVEYORS' COMPASS.
The adjustments consist of:
1. The Levels.
2. The Needle and Centre Pin.
3. The Sights.
A. L1ETZ * CO. 13
ily speaking, only the tir-t oan be nailed an adjustment, ami us this has
ed already in that of the Transit, it is not necessary to repeat it here.
I >n.l third are points which belong to the instrument-maker, but us Com-
iften subject to rough usage and liable to pet out of order, we huvo iu-
them to enable thi ih deieota temporarily.
I III. MIDII AM» <l\TI,lt PIN.
The former will very seldom require adjustment unless handled very carelessly.
As the pin has to he taken out sometimes, in order t<> sharpen it, ami in replacing
tin point will generally not return to its true position, it has to he brought again
in the centre of graduation. As each depends on the other, they must he corrected
-her.
To perform adjustment, bring the N end of the npedle on the N zero of the
compass and note the position of the S end of the needle. Then turn half way
around and bring th.' X end of the needle on the S zero of the compass, and note
again the position of the 8 end of th-' needle. If this should have changed, i. e.,
i ha\f moved either to the right or left, it is evident that the pin is out of cen-
1 must he bent. If the reading is the same, tin- pin is in the line with N and
s. ami any existing error must he corrected by bending the needle. If the
readings are not the same in amount, both the needle and pin must be bent — the
i if the reading remains on one side, and the pin most if the reading is
ou both sides.
THE NIGHTS.
The object of this adjustment is to bring the slits in a vertical position when
the instrument is leveled.
To perform, suspend a plumb line at a convenient distance and note whether it
] through the centre of the slits when the instrument is leveled. If not, correct
by tiling down the base ou that side, which is the highest. It can also be temporarily
remedied by placing paper under the lower.
REPAIR OF INSTRUMENTS.
This branch of our business has grown rapidly of late years, principally on ac-
count of the advantage Western Engineers derive from sending their instruments to
us instead of to the East.
As our location requires us to repair all the various makes of the country, while
Eastern establishments, as a rule, only repair their own, we were obliged to procure
all the material, patterns, tools, etd neceSBarv for these. Having the patterns for
all those parts which often want to be replaced when injured by falls, such as tin-
axis to the telescope, centres, etc.; facilities for cutting any threads from 5 to 100
to an inch; object glasses and eye piece lenses of any desired focus; level vials of
every diameter and length, including even the sometimes odd sizes of English in-
struments, we are prepared to do the work as economically and promptly as the
maker himself can do it. By sending their instruments to us the "Western Engineers
and Surveyors will save time and expressage.
Instruments sent to us are always thoroughly overhauled and put in as good a
condition as possible, unless directions are given specifying the repairs desired. We
believe that the best policy, insuring satisfaction and a saving of money, is to leave
it to our judgment, as there are often points appearing trivial to the engineer, but
which must be corrected if the instruments are to be relied on.
A good deal of correspondence arises to us from inquiries about the cost of
repairs, and, although it is impossible to state the exact figures, we will give a gen-
eral idea of such here.
The most costly instrument to repair is the Transit, being the most complicated.
If injured by a fall, new centers and new axis to telescope are generally required, the
cost extending from $10 to $30, or sometimes even ©50. If slightly injured, the cost
will vary from $5 to $10.
14 CATALOGUE AND PRICE LIST OF
Injuries that leveling instruments sustain from falling are generally less serious,
ranging in cost from $5 to $15. A new level vial costs from $2 to $7.50, according
to size and sensitiveness. In instruments which are defective in construction or
workmanship, sensitive levels will be a source of constant trouble and annoyance to
the engineer, and such bubbles are preferable which are in accordance with these
qualities. As a rule, we place to the better instruments levels giving for each inch
motion of the bubble an angle of two minutes: to inferior ones such giving three or
four minutes.
Compasses sent to us are principally injured by the dulling of the center pin.
Sometimes the plates and sights are bent and glass broken. Very often the center
cap is worn o\it and a new one is required. The cost of repairing ranges from $2
to $8, and sometimes even $10. A new needle, having the largest breadth in a ver-
tical direction, which is far superior to the flat style, costs $5. A new center point
costs 75 cents. A new center cap, with jewel, $1.50.
Transits and levels should always be accompanied by the leveling plates: the
legs and the head to them need not be sent. With compasses, the ball spindle should
be sent along. We advise our customers to carefully pack instruments sent to us for
repairs, as they might be sometimes injured by neglecting this precaution. When
an instrument is sent to us, a letter or postal card should always be mailed the same
day, giving us the directions and stating when the return is required.
TELESCOPES.
It is well understood that the Telescope forms a very essential part of a good
instrument; hence, it will be of interest to follow up those rules of optics which
govern the construction of such. We shall limit ourselves to the small field
required for the special class of instruments we have been describing;, and shall treat
the subject in accordance with some of the best authorities on optics.
THE FORMATION OF IMAGES BY EEJTSES AID
THEIR MAGNIFYING POWER.
When parallel rays, such as those from a star, (which by reason of their great
length may be considered parallel) fall upon a lens in a direction parallel to its axis,
the ray which coincides with the axis will pass through without suffering any refrac-
tion ; but the other rays will be refracted and found to meet at a common point in the
line of tbe axis. This point is called the focus of the lens. ^ When the surfaces are
equally convex, the focal distance is equal to the radius of tne surfaces.
When the rays fall in a direction oblique to the axis, those which pass through
the center of the lens will suffer refraction at each surface; butas the two refractions
are equal and in opposite directions, the refracted rays will finally emerge in the
same direction as the corresponding entering rays; consequently any ray passing
through the center of the lens may be considered free from refraction, as the thick-
ness of the lens is insignificant.
When the divergiug rays, radiating from a point not very distant, fall upon a
lens, the refracted rays will m eet at some point more remote than the one for parallel
rays of light — or in other words, its principal focus.
The nearer the radiant point approaches to the lens, the more the focus will recede
from it; so that when it has approached as near as twice the principal focal distance,
the focus will be at the same distance behind the lens as the radiant point is before
it, and when it has approached to the principal focal distance, the rays will emerge
parallel with infinitely distant focus.
When the principal focus of a lens is known, the formula for finding the focus
for diverging rays is, p = principal focal distance; a — distance of the radiant point
from the lens, a p
a-p
As all the rays of one point will be again refracted to one certain point by a con-
vex lens, so will the rays of a great number of points, of any object, be refracted and
formed to an image on the above described principle; and it is a universal rule that
A. Lin/ A CO.
15
when an image is formed by r eonvei Ions, it is inverted in position relatively to the
n of the object, and its magnitude i.; to that of the object as its distance from
the lens is to th.- distance ot the object from the Lena.
If '/ b is an object placed before the convex lens m m, every point of it will send
forth rays in every direction. Those rays which fall upon the lens m m will be
refracted to a foci behind the lens, and at such a distance from it as may be deter-
mined by the above formula.
The point a will send rays to every point of the lens, one of which will pass
through the center woi it, hence will not suffer any refraction; consequently the point
«' of the image representing the point'/ of the object must lie somewhere in the
continued line a V — that is. where the refracted rays a m meet this line. In the same
way the rays of the point b or any point of the object will be refracted, so that ft'
represents <t and b\ b of the object, whose image is consequently inverted.
As the angle a v b is equal to the angle a v' b\ the length of the object a h must
be to the length of the image <>• // as the distance of the object a b from the lens
>n m is to the distance of the image a' b' from the lens m m.
The brightness of the image will always depend on the brightness of the
object; when the brightness of the object increases, the brightness of the image will
increase proportionately. It is also evident that we may increase the brightness of
the image by increasing the size of the lens, or the area of its surface. If a lens has
an area of 12 square inches, it will obviously intercept twice as many rays proceeding
from every point of the object as if its area were only G square inches.
If we place the eye about G inches 'the distance at which a normal eye will see
small objects most distinctly) behind the image «' 6' we will see the same very clearly
and distinctly, apparently suspended in the air. The cause of this will be readily
understood if we consider that all the rays which form by their convergence the
points a' b' of the image, cross one another at a' b\ and diverge from these points
exactly in the same manner as they would do from a real object of the same size and
brightness placed in <<' 0'.
The image a' b\ therefore, may be regarded as a new object; and by placing
another lens behind it, another image of the image a' b' would be formed, exactly of
the same size and in the same place as it would have been had <t' b' been a real object.
Since the new image a' 6' must be inverted, this new image will now be an erect one
of the object a b, obtained by the aid of two lenses; so that by using one or more
lenses we can obtain erect or inverted images of an object at pleasure.
In order to explain the power of lenses in magnifying objects, or rather in giving
magnified images of objects and bringing the image near us, we must examine the
different circumstances under which the same object appears when placed at differ-
ent distances from the eye. •
If the eye looks at a man placed at a distance, his general outline only will be
seen, and neither his features uor his dress will be distinguishable. "When he is
brought gradually nearer, wo discover the different parts of his dress; till at a dis-
tance of a few feet we perceive his features distinctly.
The nearer an object is to the observing eye, the greater the angle will be under
which it is seen ; and the apparent magnitude of an object can, therefore, always be
measured by the angle at which it is seen.
16 CATALOGUE AND PRICE LIST OF
Suppose an object be placed at a distance of 100 feet from the eye, and a lens of
25 feet focal length be placed half way between the object and the eye — that is, 50
feet from each — this lens, as previously shown, will form an image of the object 50
feet behind it of the same size as the object. If this image is looked at by the eye
placed six or eight inches behind it, it will be seen exceedingly distant, and nearly as
well as if the object had been brought from a distance of 100 feet to a distance of six
inches, at which we can examine minutely the details of the object.
Now in this case the object, though not actually magnified, has been apparently
magnified, because its apparent magnitude is increased in the proportion of 100 feet
to six inches, or 200 to 1.
"When the focal length of the lens is quite inconsiderable, compared with the
distance of the object, as it is in most cases, the proportion of magnifying power
will be considerably changed, compared with the preceding illustration, on account
of different foci at different distances.
Suppose a lens of one foot focal length forms an image of an object 1000 feet
distant, this image would be formed at very nearly the distance of the principal focal
length from the lens. If we could now place the eye in the center of the lens, we
•would necessarily see from this point the image at the same angle as the object would
appear on the other side; hence, the apparent magnitude of the image would, when
viewed from a place one foot distant from it, be the same as that of the object when
viewed from the center of the lens, although actually diminished 1000 times. But
as a normal eye can have a distinct view of an object at a distance of six inches, we
can also approach to this distance from the image formed by a lens, and still see it
distinctly. The apparent magnitude of the image then observed will be twice as
large as the object appears when, viewed from the center of the lens, and conse-
quently the object will appear twice magnified.
In the ease of a very short-sighted person, who sees objects distinctly at a dis-
tance of three inches, the magnifying power would be four.
From this, the rule for finding the magnifying power of the lens, when the eye
views the image which it forms, is: Divide the focal leugth of the lens by the dis-
tance at which the eye obtains a distinct view of the image.
Here, then, we have the principle of the simplest telescope, which consists of a
lens whose focal length exceeds six inches, placed at one end of a tube whose length
must always be equal to the focal length of the lens, plus the distance for distinct
vision.
But there is still another way of increasing the apparent magnitude of objects,
particularly of those which are within our reach.
It is proved in optics that a good eye can see distinctly when rays of light par-
allel, or nearly so, fall upon it, as it has the power to accommodate itself to objects
at different distances. .
If we bring an object, or the image of an object, very near to the eye, so as to
give great apparent magnitude, it becomes indistinct, as the rays of light which pro-
ceed from it diverge lo such a degree as to render the eye unable to accommodate
itself to them; but if we can, by any contrivance, make the rays enter the eye nearly
parallel, we shall necessarily see the image distinctly.
But we have already shown that when rays diverge from an object placed in the
focus of a lens, they will emerge parallel. If we, therefore, place an object or an
image of one in the focus of a leus, held close to the eye, the rays will enter the
eye parallel, and we shall see the object distinctly. The present short distance of
the image to the eye is equal to the focal length of the leus, so that the magnifying
power produced by it will be equal to six inches, divided by the focal length of the
lens, consequently the shorter the focal length, the greater the magnifying power.
"When a lense is used to magnify the image produced in a single lens telescope
from a distant object, the two lenses together constitute what is called the astrono-
mical telescope.
MAGNIFYING POWER OF TELESCOPES.
Every telescope consists of two distinct parts; the object glass forming the image
and the eye piece by which this image is viewed and magnified.
Although the different kinds of telescopes differ in the construction of their eye
pieces, they are yet subject to the same rules in regard to magnifying power, field
A. L1K1Z A CO. 17
and light; we will therefore illustrate these rules in the most simple manner, to avoid
'm trouble of tracing the tight through two, three or more lenses, and describe
separately.
We have previously shown that, when viewing an image from a place as far
distant as the focal length of the Lens by which it is formed, it will have the
rent magnitude as the object, and by placing a lens between the image and the
l SUCh a manner that the focus of the lens will be in the same plane with the
it distinctly by placing the eye close to the lens.
As the rays <>f light diverging from the focus of the lens emerge parallel, we see
placed in the focus Of a lens at the same angle as it would be seen from
tin center of this lens; ami as the apparent magnitude Of an object increases in
proportion to the decreasing of the distance at which it is viewed, the rule for finding
the magnifying power of an astronomical telescope with single lens eye piece, is:
Divide focal length of object glass by focal length of eye piece.
By this rule it is evident that a telescope with a long focal length object glass,
ami an eye piece of very short focal length, will magnify very much, but experience
has shown that unless certain limits should be maintained, such a telescope would,
by (he loss in size of tiehl and light, be rendered useless.
FIELD OF TELESCOPES.
The field of view of a telescope is always measured by the angle which the
object visible through it subtends to the eye. Should the moon, for instance, just
rill the field of a telescope, the field would be half a degree, as the moon subtends
that angle when viewed with the naked eye.
Two lines drawn from the outer edge of the lens n n (in above figure, m m rep-
resenting the object glass, n i> the eye lens) to the center v of the lens m m, and con-
tinued would just cover the object A fi. Suppose these lines .4 v and B u to repre-
sent the rays of light sent from the points A and B of the object through the center
v of the lens m r», they will be incident at the very margin of the lens n n, thus the
points A and B can just be seen through the telescope, while the points a and b can
not, as the dotted lines a o and b u indicate. Therefore, the angles A v B or n >■ »
are the greatest that can be seen through a telescope, and consequently constitute its
field.
It is evident now that the size of the object glass does in no way contribute to
the size of the field of view, but that the same may be increased by enlarging the eye
lens or shortening the focal length of the object glass.
We have previously seen that in order to increase the magnifying power of a
telescope by means of the eye lens, we must shorten its focal length; at the same
time experience has shown that the diameter of the aperture of this lens must not
exceed half its focal length, as otherwise the spherical aberration of such a lens
would distort the image to a very annoying degree, which error necessarily must be
avoided.
By this rule the field of view is always fixed for a single lens eye piece. For
this reason and others, which will be explained under the heading of " Eye
Pieces," a combination of two lenses is used with the improved astronomical
telescope. Two lenses of equal focal length, combined, will act like one lens of
half the focal length of each; the aperture of each lens being half its focal length,
the two combined will, therefore, afford twice as large a field as a single lens of the
same power.
2
18 CATALOGUE AND PBICE LIST OP
LIGHT TRANSMITTED RY A TELESCOPE.
It is at once perceived that the quantity of light entering a telescope is depen-
dent upon the size of the object glass or its aperture; the larger its area of surface,
the Tit ore rays of light proceeding from every point of the object will be intercepted
and transmitted.
Z M and z m are the outward rays of all those radiating from a distant point, and
intercepted by the lens Mm ; they are refracted to a focus at/, forming the cone M
fm, which receives all the light contained in the cylinder Z M z m ; from point/
they will diverge again, forming the cone Nfn , of which a part of lens N n forms the
base; as the point/ is the common focus of both lenses, the rays will emerge parallel
from Nn forming the cylinder N i n k.
Evidently the light contained in the cylinder N in k is more dense than in
Z ni zm ; the degree of density is reversedly proportional to the square of their vertical
section. The diameter Kn is to the diameter Mm, as the focal distance icf to the
focal distance vf, or as we have previously seen, as one to the number of times the
telescope magnifies; hence the diameter Mm divided by the diameter N n will give
us the magnifying power.
This rule remains the same with all telescopes, the eye piece may consist of one,
two, or four lenses.
By placing the eye a few inches from the eye piece of any telescope, the pencil
or cylinder of light Ni n k will appear as a bright speck, diameter of which may be
very closely measured by means of a finely graduated rule; divide by this diameter
the diameter of aperture of the object glass, and the quotient is the magnifiying
power of the telescope.
In order that the whole pencil of light, N in k, may be received by the eye, its
diameter i h must not exceed the diameter of the pupil of the eye, because being lar-
ger, a part of it could not enter the eye, and consequently part of the light intercepted
by the object glass would be lost.
The diameter of the pupil is, as found by experiments on an average 1-10 of an
inch, hence the construction of a telescope should aways be so, that i k does not ex-
ceed 1-10 of an inch in diameter. Taking r to be the magnifiying power of a tele-
scope, the vertical section i k is r times smaller than Z z ; the square of i k, conse-
quently, is r r times smaller than the square of Z z ; hence the brightness of light r r
time greater at i k than at Z z.
According to this it would seem as though objects were seen r r times brighter
through a telescope than with the naked eye; but, considering the telescope as mag-
nifying the diameter r times, and the square surface r r times, the r r times increased
light will again be r r times decreased.
Therefore no combination of lenses is possible, by which the brightness of an ob-
ject would appear greater than when viewed with the naked eye under the same angle
of sight.
We mentioned above, that the diameter i k should not exceed 1-10 oi an inch, in
order not to lose any light; therefore a telescope constructed thus, to make the pencil
i k 1-10 of an inch in diameter, would, in regard to brightness of image, give the best
result, as the diameter i k would be equal to the diameter of the pencil of light, inter-
cepted by the pupil when viewing with the naked eye.
\. una a i;t
- smaller than 1-10 of an inch, the brightness of the object will
> than when Tiewed with the naked eye, as in the fatter case the eye would ro-
under of light; the brightness will obviously decrease in the
>rtion as the square snrrac smaller than the square Burfaee oi
the pupil.
brightness of view is an indispensable requisite of a good telescope, the
ifying power should never l>e raised to an excessive degree, especially with U r-
iten used for view in nly faintly illumiu-
riinenta have shown, and it is uuiversally admitted iu opti
that the magnifying power may be increased to such ad (give the penci
only 1-20 to 1-24 of an inch diameter, before the eye will perceive a sensible diminution
uf liu'ht; tbis limit however, should n eded.
tope, magnifying thirty times, will shew an objeot only <■
bright »t it distance ?tt 900 feet, as when viewed from a distance of thirty feet with
the naked eye; the reason for this is, the power of absorbing light possessed by all
bodies; even the air, th> isparent body iu nature, is capable of absorbing a
quantity ol light. On the summit of the highest mountains, where their light
through a much less extent of air, a much greater number of stars is
visible to the eye than in the plains below. Glass is a medium of still greater ab-
sorbing power than air. Each refraction of light is also connected with more
is "f light, through the existence of very small imperfections in the surfaces
of even the most perfect of lenses, and which cause reflections and dispersion of
light.
In the above instance the rays of light intercepted and transmitted by the tele-
scope have to puss through 870 feet more of our atmosphere, through three (astron-
omical telescope I, or five ( terrestrial telescope) thicknesses of glass, and suffer six or
ten refractions before entering the eye, whereas the light intercepted by the naked
eye only passes through thirty feet of our atmosphere.
"When the naked eye is viewing an object, for instance, large and well-defined
black print on a white ground, faintly illuminated, it must approach to within a cer-
tain distance, in order to read the print, and see every line distinctly; if twice as
much light is now turned upon the object, the eye may recede to nearly twice the
distance as before, and still see the print as distinctly as in the first place; if the
object is very brilliantly illuminated, the eye may recede to a considerable distance
further from the object, and still read with the same distinctness.
In nearly in the same proportion may the eye, viewing through a telescope,,
recede from the object, as the brightness of the object increases.
If, in the above instance, the distance at which the eye may obtain a distinct
view of the object is 6 feet at first, a good telescope mngnifiying 30 times, would, at
nearly 180 feet show the object equally distinct and bright, to equal the distinctness
of view- from the second position of the naked eye, the distance being about V2 feet,
the telescope could recede to a distance of about 360 feet, while, in the last instance,
when the object is brilliantly illuminated, and the naked eye may see distinctly from
a place 60 feet distance, the telescope would afford the same view, from a place about
1. suit feet distant, or, after making a liberal deduction for loss of light, at about
1,500 feet distant.
It is therefore evident that it would be absurd to use the distance at which any
certain object can be seen distinctly through a telescope, as a measure for the quality
of the same, without defining the brightness of the objeot, and also the state of our
atmosphere at the time of observation; but, as this with naturally illuminated objects
is very uncertain and difficult, it leaves large margin for exaggeration.
AU the above comparisons with the naked eye presuppose a normal eye, which
can see distinctly very small objects at a distance from 6 to 8 inches.
SPHERICAL. ABERRATION OF I.EXSKS.
We have heretofore assumed that the rays refracted at spherical surfaces will
meet exactly in a common focus; but this is by no means strictly true.
The rays incident near tbe axis of a spherical surface, or of a lens, are refracted
to a focus more remote from tbe lens, than those which are incident at a distance
from the axis; therefore an image formed by an ordinary lens, is clear and distinct
in the centre, but grows faint and indistinct at the edge.
20 CATALOGUE AND PRICE LIST OF
In using a lens of different radical curvatures, or a piano convex lens, for form-
ing an image, it is by no means immaterial which side is turned to the object. A
plane convex lens, with its plane side turned to a distant object, will produce nearly
four times as much spherical aberration as if its convex surface is turned to
the object. For magnifying a near object, its plane surface must be turned to
the object.
In using a piano convex lens, therefore, it should always be placed so that
parallel rays either enter the convex surface or emerge from it.
The lens which has the least spherical aberration is a double convex one, whose
radii are as 1 to 6. When the face whose radius is 1 is turned towards parallel rays,
the aberration is only 1.07 of its thickness — that is, when the two surfaces meet in a
sharp wedge, and the whole area of surface is used.
By reducing the diameter of the same lens by covering up the outer parts of it
■with a ring of black paper, the aberration will be greatly diminished; therefore the
aberration will obviously increase with the diameter of the lens when its curvature
remains the same.
The diameter of lenses used for forming an image should not exceed one-seventh
of their focal length, or the angles which the lens subtends to its focus should not ex-
ceed 8 or 9 degrees.
But, though the spherical aberration of single lenses cannot be removed or
diminished beyond a certain limit, yet, by combining two or more lenses and mak-
ing opposite aberrations correct each other, this defect can be remedied to a very
considerable extent in some cases, and in others altogether. Correct calculations
for the spherical aberration are, in the construction of any optical instrument, of
great importance.
CHROMATIC ABERRATION OF L.ESJSES.
"White light, as emitted from the sun, or from any luminous body is composed
of seven different kinds of light, viz: red, orange, yellow, green, blue, indigo and vio-
let; called the primary colors of the prismatic spectrum. This compound light may
be decomposed or analyzed by refraction. A ray of white light incident upon the
surface of a lens will not only be refracted, but also split into its prismatic colors.
As these colored rays have different degrees of refrangibility, or different indices of
refraction, it is evident that all the rays which compose the incident ray of white light
cannot possibly be refracted in the same direction, so as to meet at one point; the
formation of an image is therefore imperfect.
The focus of the extreme red ray with the index of least refraction will be more
remote from the lens than that of the extreme violet ray, which has the greatest
index of refraction, the intermediate rays having their foci at intermediate points
between the two.
Therefore, the image of any luminous point consists of as many colored images
as there are colored rays contained in white light; so that if we place the eye behind
it, we will see a confused image, possessing none of that sharpness and distinctness
which it would have had if formed only by rays of one color.
The combination of both spherical and chromatic aberration will, therefore,
render an ordinary lens useless for forming an image, unless possessed of a very
long focal length with a comparatively small aperture.
ACHROMATIC OBJECT GLASSES.
One of the greatest inventions of the last century was that of achromatic lenses,
which destroy the chromatic aberration.
They are formed by combining two lenses, a double convex crown-glass lens and
SL7iearlypla.no concave flint-glass lens; the inside surfaces are ground to the same
radial curvature; as the concave lens has a longer focal length than the convex one,
the combination still acts like one convex lens.
The proportion of their focal lengths is so calculated that the dispersion of light
caused by the crown-glass lens is corrected by the flint-glass one.
The counteraction of the dispersion of light of one lens by means of another is
a result of the difference of dispersive power, at the same mean refraction, of the
two different kinds of glass.
A. LXBTZ & CO. 21
Suppose a ray of light incident upon ft doubh -; this ray, aa we have
will be split into s< ven different colored rays having different degrees of refran-
ribility, and will, therefore, foous at different points bom the lens. If we now place
1 this h ns n donbli :i> ..f the same material, having its surfaces ground
t-> the same radial onrvatnre, it is obvious that the refracted colored rays, converging
to their respective foci, will again be refracted, to emerge parallel from the eoncave
As the two refractions were equal, bnt opposite to one another, the dispersion
of light caused by the first refraction is certainly corrected by the second one, and
white light will finally emerge. Bnt it is also evident that the combination forms a
of glass whose faces are parallel, the outer surface of the convex lens being
parallel to the outer surface of the eoncave one.
Though we have thus corrected the colors produced by the convex lens by means
Of the eoncave one. we have done this by a useless combination, since the two
Combined act only like a piece of plain glass, and are incapable of forming an image.
If we make the concave lens, however, of a longer focus than the convex one,
the combination will act as a convex lens and will form images behind it, as the rays
will converge to a focus behind the concave lens; and if we make it of another ma-
terial having a greater dispersive power at the same mean refraction, we are able to
correct the colors also.
The dispersive power of crown glass is to the dispersive power of flint glass as
1 to 1.8703. (This proportion varies somewhat with different glasses.) If we,
therefore, combine a convex crown-glass lens of one inch focus with a concave flint-
1 8703 v I
glass lens of 1.8703 iuch focus, this combination, having a focal length of v-tt - t^^ r =
2.149 inches, will refract white light to a single focus free of colors.
Such a lens is called an nrhromatic lens, or when used for forming the image in
a telescope achromatic object glass.
The dispersion of light can, however, by a double lens never be complete!]/ cor-
rected, as the equal spectra formed by the crown and flint glass are not in every respect
similar; the colored spaces in the one are not equal to the colored spaces in the other ;
therefore, only those outer rays of the prismatic spectrum are completely corrected,
upon which the calculation is based for finding the focal distance of the two lenses,
while it leaves a slight degree of dispersion for the intermediate colored rays, thus
forming the secondary colors of the prismatic spectrum. These are iusignificant if
the lens is otherwise perfect and of good workmanship.
In mounting the two lenses of an object glass iu the cell, it is of great importance
to get the axis of the two lenses to coincide. Gross neglect of this important rule is
very often the cause of indistinctness of image. Another important requisite is to
keep the inner surfaces slightly apart by means of three equally thick pieces of silver
or tinfoil placed at the very margin, at equal distances between the two lenses. By
neglect of this rule colored rings will be produced upon the surfaces.
The first of the above mentioned results is only attainable by the instrument
maker. After the two lenses are carefully cleaned and properly placed in the cell,
with little pieces of silver foil between them, which must be fastened with the least
moisture of gum arabic.
By taking the lenses apart the centering of the same is disturbed, and the engi-
neer is unable to replace them properly, especially when they tit loosely in their cell,
which is very often the case. The staining of flint-glass lenses is caused by the cor-
rosion of the oxide of lead contained in the glass. Generally, however, it will only
occur when the leus is kept in a damp place for some length of time.
In cleaning an object glass, care should be taken not to rub it any more than is
necessary. Brush oft' the dust first with a camel's hair brush or a soft piece of worn-
out linen, and then wipe it carefully with a clean piece of chamois leather. When
very dirty wash it with alcohol or water and soft chalk, being careful to have the
chalk free from grit.
EYE PIECES OF TELESCOPES.
"When an inverting or astronomical eye piece is used in surveying instruments,
it is generally the so-called Bamsden Fye Piece. It consists of two crown-glass
lenses, placed at such a distance as to correct the chromatic aberration of one lens
by the other.
22 CATALOG OE AND PEICE LIST OF
A ray of white light proceeding from the achromatic object glass will be refracted
by the first eye piece lens and split into different colored rays; bat these rays, being
intercepted by the second lens at different distant points from the axis, will suffer
different degrees of refraction.
The extreme red ray, with the index of least refraction, will be intercepted by
the second lens at a point more distant from its axis than the extreme violet ray;
therefore it will suffer a greater refraction than the violet one, notwithstanding its
inferior refrangibility; so that the two rays will emerge parallel from the second lens,
and therefore be colorless.
The erecting eye piece in general use consists of four crown-glass lenses, placed
also at such distances as to correct the chromatic aberration. In this eye piece
the inverted image of the object glass is again inverted, and an erect image is formed
between the third and fourth lens, which is viewed and magnified by the fourth lens.
This form of eye piece, however, is inferior to the astronomical or inverting eye
piece, owing to the loss of light it must suffer through obliging the light to pass
through two more lenses.
At the same time the inverting eye piece allowsalonger focal length object glass,
which is very important in correcting spherical aberration.
For these reasons this eye piece is universally adopted in Europe for all survey-
ing instruments, and we are perfectly convinced that it would also be preferred by
our own engineers if they would accustom themselves to its use. It may seem incon-
venient at first to work with an inverting telescope, but in a remarkable short time
this difficulty is entirely overcome, and the work may be done with the same rapidity
and certainty as with the erect one.
As the erecting eye piece is in general demand, we do not intend to introduce
the inverting one, but, we think, however, that the professors of civil engineering in
our colleges should draw more attention to the above facts, as gratifying results may
be often obtained by the use of this eye piece with no material inconvenience.
We have previously seen, that by increasing the diameter of the eye piece lenses,
we may enlarge the field of a telescope. In the erecting eye piece (Kellner Eye
Piece) which we use in our telescopes, by inserting one achromatic lens, in place of
a plain one. the formula is so changed as to permit the use of lenses of larger diam-
eter, and thus increase the field considerably, compared with the ordinary eye piece
of the same power.
In constructing a combination of crown glass lenses to be used for magnifying
objects, the spherical aberration can easily be reduced to its minimum, by giving
each lens its proper curvatures and position, while the chromatic aberration is far
more difficult to overcome without the use of achromatic lenses; therefove, before
achromatic lenses were invented, refracting telescopes had to be made of enormous
length, with comparatively very small aperture of object glass, in order to reduce the
chromatic aberration.
On the same principle the Kellner Eye Piece is improved by the use of achrom-
atic lenses; it is, however, nothing new, and the only reason for its not being uni-
versally adopted in first class telescopes is, undoubtedly, its extra expense to the
instrument maker.
TRA.STSIT TELESCOPES.
After having viewed the optical rules, which govern the proper construction of
a telescope, the mechanical part will be easily understood.
The slide to which the object glass is attached fits directly in the outside or body
tube. Particular attention is paid to this part, to prevent even the slightest shake,
and still procure an equal and smooth motion, which is absolutely necessary, as other-
wise no true adjustment for line of collimation is possible.
The slide is movable by a rack and pinion, to permit a precise focusing of the
object. A slide protector is furnished with each Telescope.
The cross-wire frame is suspended in the tube by four capstan head-screws, by
which it is also adjustable. The frame is so constructed that the cross- wires cannot
be torn, in case the adjusting screws are tightened too much.
The spider's web, used for the cross-wires of our instruments, is always properly
treated to avoid all twist, and prevent lengthening and becoming crooked in damp
weather, and is well secured to prevent its coming loose. (See page 28 — Glass Diaphragms, )
a. i.ieiy a 23
oleaa specially d as to permit
isary, by simply anscrewing it. In replacing, ii should always
ip. It is movable in and out by o revolving motion, turning th
m back or forward, a manner which affords a finer and
nd pinion is oapable of doing.
With our high power eye-pieces, a motion of only about three-sixteenths of au
i allow for uifferenoe ol eyes.
As the sliding motion of the eye-piece is only to allow for the difference of eyes,
it is not at all necessary to disturb it after it is once properly set, as Long as tfa
J >n is using the instrument; and even in packing it away in the box it may be
>, as we always allow for this extra motion in packing the instruments. The
eye-piece cap is provided with a Blide to protect the eye-lens fromdnsl while the
instrument is not in use; the engineer should never neglect to close up the eye-piece
and also cover the Object glass with its cap, as soon as the instrument is set at rest.
Considering that, iu cleaning, each rub will destroy more or less of the fine
finish of the lenses, upon which dep< nds the biightness and brilliancy of the image,
pneer will be well repaid for his care in this particular.
I.I MO OF < OIJ.IH ATIOY.
The line of collimation in transit telescopes la & perpendicular line drawn from
the center of the object glass upon the axis, or center of motion of the telescope; to
the other end of this line the veitie.il cross-wire must be adjusted, thus marking this
line in the field of view of the telescope,
As the line of collimation is a perpendicular line upon the axis, the slide by
which the object-glass is moved in and out must also be perpendicular upon the
as otherwise the adjustment for long distances would not be true for short ones.
To obtain n correct adjustment for long and short distances, it is also necessary
that the Itm •>/ collimation shall lie in the same plane us the vertical center of the
instrument.
If the line of collimation is adjusted for long distances and the slide not perpen-
dicular to the axis, the center of the object-glass will be shifted obliquely to this line,
when moving it out in order to focus a near object, and thus a new line of collimation
parallel to the first one is formed for short distances, sometimes causing very serious
errors.
In some telescopes the slide is adjustable in the same manner as the eye piece
guide-ring by four screws. The principle of this adjustment is very good, but practi-
cally it is very objectionable, as the constant friction upon the ring will work it loose,
after which nothing but a loose ring guides the slide; au attempt to correct it will be
found most difficult, as there is no way of defining the value of the error, in reference
to the adjustment, and, also, the inverted position of the image will confuse the en-
gineer so that it will be abandoned before a true adjustment is obtained. The only
effective manner in which to produce a true slide for the object glass is by good work-
manship, without any adjustment whatever.
The above error may also be caused by crooked tubes; but a more frequent oc-
currence is shake in the slide. If this is the case, there is no true adjustment for line
of collimation possible, as the slightest turn of the milled pinion head will throw the
object-glass to one side or the other.
This defect can only be remedied by a competent instrument maker.
LEVEL TELESCOPES.
Our Level Telescopes are in every respect, except size, similar in construction to
our Transit Telescopes.
In Y levels the telescope rests on two very hard bell metal rings, or collars, which
are soldered fast to the tube, and it is reversible, end for end, in the Y's.
The iwy first requisite of a Y Level Telescope is to have these two rings of exactly
equal dfamtter, and perfect cylinders. If they are of uuequal diameter, the line of
collimation, when the bubble indicates a horizontal position, will not be parallel
with a tangent to the curve of the bubble at its highest point, and, therefore, no true
level can be taken with such an instrument.
24
CATALOGUE AND PEICE LIST OF
It is very often believed that, in the course of adjusting the Y level, by reversals
of telescope and revolving on center, (see Level Adjustments), the bubble will show
up any inequality of the collars. This is by no means true.
If the Y's are both filed out to the same angle (which is generally the case, or at
least very near so, as they are by most all instrument makers filed out by gauges),
the inequality oi the collars maybe ever so much and the instrument will still be adjust-
able in all its parts; that is, the instrument may be so adjusted that the bubble on all
reversals, end for end, of the telescope, and revolving on center, will always give the
same reading on both ends — that is, indicate a true horizontal position.
A final test is, therefore, necessary after the instrument is properly adjusted,, to-
ascertain the equality of the collars.
Make two bench marks, place the instrument exactly midway between, amd find
the true difference of level between the two by reading leveling rods set upon them.
Now place the instrument near one of the bench marks and read both rods. If the
difference of the readings obtained now is equal to the true difference of level, then
the collars are of equal diameter, and the line of colHmination is at a right angle to
the vertical center of the instrument.
If the distance at which this test is made be so long as to make corrections for
eurvature and refraction necessary, the difference of the readings with a true instru-
ment would be equal (when placed near the higher bench mark) to the true differ-
ence of level plus correction for curvature and refraction for the distance at which
the rod on the lower bench mark is viewed.
When the instrument is placed near the lower bench mark, the difference of the
readings must be equal to the true difference of level, minus corrections for curvature
and refraction.
If the line of collimation is thus found to be at right angles to the vertiele centre
of the instrument, then this test, once made, is good forever, as it shows that the
collars are of equal diameter; and, consequently, a true adjustment may be made in
the manner described with level adjustments.
It need hardly be mentioned that denting, the settling of dirt on the collars and
unequal wear will also affect the adjustment in the same manner.
If the test shows that the line of collimation is not perpendicular to the vertical
centre, then the collars are of unequal diameter, and the instrument is virtually
nothing more nor less than a dumpy level, as this defect deprives it of all the advan-
tages for an easy and convenient adjustment, which characterize the Y Level in com-
parison with the dumpy.
The effectual remedy lies only with competent instrument maker.
But the defect may also be temporarily remedied or adjusted in the same
manner as the line of, collimation in the dumpy level is adjusted.
Establish a true level line as described in above test; place the instruments be-
yond one bench mark, and, by means of the parallel plate screws, bring the line of
collimation in a true horizontal position; then raise or lower the adjustable end of the
spirit level whatever may be necessary, until the bubble gives the same reading at
each end. Now, the line of collimation is parallel with the bubble; that is, with
the tangent to the curve of the bubble at its highest point. To place the line of
collimation at right angles to the vertiele center, place the telescope over a pair of
parallel plate screws, and, by turning them, bring the bubble to the center; reverse
the instrument about its vertical center as near 180° as possible; correct half the
deviation of the bubble by raising or lowering one of the Y's, and the other half ty
means of parallel plate screws; repeat the operation until the bubble will give the
same reading at each end in any position of the telescope during and entire revo-
lution on the vertical center.
The telescope must now remain permanently in the Y's, as it would, if reversed
end for end, double the error which existed previous to this adjustment.
The adjustment may also be made by placing the instrumeut beyond one bench
mark, leveling it up and then simply changing the position of the horizontal cross-
wire by means of the capstan head screws to the place which will make the line of
collimation truly horizontal, and at the same time be parallel with the spirit level,
which was placed at right angles to the vertical center previous to this test. The
instrument will then be in true adjustment.
A. LIETZ & CO. 25
The disadvantages of this adjustment, compared with the proceeding One, is
that the lint- of eoDimaiion will not 1m- parallel with the optica] axis of thetelesoope ;
and, furthermore, the object glass slide, being made to glide parallel with tin- optical
will not more parallel with the line ol oollimationi ami, for the smut- reasons
ren with lint of collimation of Transit Teh scop, s, the adjustment will not agree
on Bhort dista n c e s. Another advantage of the first adjustment is in its preserving
the facility of overhauling the cross win adjustment by turning the telescope round
its longitudinal axis. Tin- other adjustments, being stable ami strong, remain
perfect for a long time, while tin oross wire adjustmenf is more easily deranged than
any other, and, therefore, nee. Is frequent inspection.
We have carefully explained this defect, owing to the conviction on our part
that it is a much more common one than is generally suspected. Numbers of cases
have come und-r our observation where the defect existed in a remarkable degrei
We are aware that correct leveling may be doue with a level entirely out o£
adjustment by taking the utmost precaution for equi-distant sights. But looking at
it from this point of view, why not use the dumpy level then, instead of the more
COStly Y level !
Upon perusing the numerous works on engineering and surveying, we notice
but very few which mention the above defect, and still fewer which give a correct
test for it.
TEST OF TELESCOPES.
If a telescope is to be tested for its qualities, make sure first that all the lenses
are perfectly clean.
To test a telescope for its definition, small clear print should be used, and viewed
from a distance of about 30 to 50 feet. If the print appears clear and well defined,
and fully as legible at this distance as if viewed with the naked eye at the distance
for distinct vision, the surfaces of the object glass are perfect and well finished. If,
on the contrary, the print appears dull and indistinct, and the fine details illegible or
even invisible, the surfaces are imperfect and not truly spherical, as the rays pro-
ceeding from each point of the object are not refracted to their corresponding points
in the image.
Indistinctness may also be caused by spherical aberration.
To test this, cover the object glass with a ring of black paper, reducing the* aper-
ture to one half; focus small print to distinct vision; remove the ring of black paper
and cover the center of the object glass (previously left open), then mark how much
the object glass has to be moved in or out for distinct vision.
"When the spherical aberration is reduced to its minimum, very little if any slide
motion is necessary to obtain a distinct view under both tests. The amount of shift
is, however, a measure for the spherical aberration of the object glass.
Another test, but not as good as the one above, is to focus the object to distinct
vision, and then moving the object glass in or out by means of the milled pinion
head, at the same time observing how much motion is necessary to render the object
indistinct. If the spherical aberration is completely corrected, the object should,
theoretically, be rendered indistinct by the slightest motion in or out; but, practi-
cally, it is not, as the eye will accommodate itself to a certain degree to the difference
of divergence of the rays, which is caused by the motion, in or out, of the object
glass, in the same manner as it will accommodate itself for near and distant objects
when viewing without the aid of lenses.
So, if the image formed by a perfect object glass is viewed by another perfect
lens of long focal length, say 6 inches, the object glass might be moved in or out
one-fourth of an inch from the point of distinct vision, and the object will still
appear comparatively distinct, as the one-fourth-inch motion, with an eye lens of
such long focal length, cannot cause enough difference in the divergence of the rays
to prevent the accommodation of most eyes to it. The shorter the focal length of
the eye lens, the more rapid will be the change of divergence or convergence of the
rays with a certain amount of motion; therefore the second test is only applicable
with eye pieces of very high power, which at the slighest motion in or out, will cause
a sufficient amount of divergence or convergence of the rays to prevent the accommo-
dation of the eye to its change.
To test the chromatic aberration, either a celestial body or a white disc should be
selected for an object.
26 CATALOGUE AND PRICE LIST OF
Focus the object to distinct vision, and then move the object glass slowly in and
out alternately. If, in the first instance, a light yellow ring is seen at the edge of the
object, and in the second one a ring of purple light, the object glass may be con-
sidered perfect, as it proves that the most intense colors of the prismatic spectrum
(orange and blue) are corrected.
To test th& fltttness of field, take a square fiat object, not around disc, whose sides
are about 4 inches long and perfectly straight — the best object is a heavily lined
square, drawn on white paper with India ink. Sight this object from such a dis-
tance that it will nearly fill the field of view of the telescope, and see if it still ap-
pears flat and its sides perfectly straight; if so, the telescope is a good one. If, on the
contrary, the object appears distorted; i. e., if the sides, instead of being straight,
form curves and the surfaces appear concave, instead of fiat, the telescope is not
good, as it shows that the proportions of foci, aperture and distances between the
different lenses are not according to the laws of optics, owing, generally, to the at-
tempt to force the magnifying power beyond its limits.
As all the refractions of light in the telescope are caused by flat and spherical
surfaces, it is evident that the edge of a round flat object, when used for above test,
cannot be distorted, but that only the surface will appear concave to a keen observ-
ing eye.
A Telescope which distorts the image to a perceptible degree, will, however,
not cause any errors in common use, but is decidedly objectionable for stadia
measurements where two points in the field of view are used at the same time.
STADIA MEASUREMENTS.
Having given an account of the different methods for measuring distances in
another part of this book, we will treat the method termed stadia measure-
ments more at length, as it is the most superior, in our belief, and one which
will, in time, supersede all others, except chaining, of which it will always be a use-
ful companion.
After having read the article on the " Formation of Images," the principle will
be readily understood.
The length of image of a certain object, whose length and distance are known, is
marked in the field of view by two extra cross-wires, equally distant from center
cross-wire. The distance between the two wires may thus be used as a measure for
finding the distance of any objects whose length is known.
The laws of dioptrics teach us that the length n of an image formed by a convex
p h
lens may be ascertained by the following rule: n= —
a-p
p — focal length of object glass.
h — length of object.
a— distance of object from the center of object glass.
This formula shows at once that the greater the distance a the smaller will be
the image n.
"We learn, furthermore, that the distance b from the image to the center of ob-
ap
ject glass, using the above sign, is — -
a-p
This formula readily shows that a change in the distance a changes the distance b
considerably, especially when distance a grows very small and becomes nearly equal
to distance/).
Therefore, as a change in the distance a also changes the distance b, the image n
of the object h (in the cut below) cannot grow smaller in proportion to the increase of
distance a. We must, consequently, find a correction for the error which would be
caused by making the center of the object glass the starting point for the measure-
ments.
In the cut below, p — focal length of object glass.
h — length of object.
a— distance of object from center of object glass.
b — distance of image " " " *' "
n — length of image.
lietz i 27
p h p h h h a-p
— — - therefore a-p= — or — p=ap or — = —
<»-/'. n, n /-.
Therefore the image is as many times smaller than the object as the focal length
ssi by which this image is formed), is contained in the distance from
the object to a point one focal length in front of the object glass; consequently, this is
the true Starting point for all stadia measurements.
The Telescope must also be first-class in regard to power, definition and light, to
» nahle the taking of long sights correctly without the use of two targets to rod; the lat-
ter style, however, insures a greater accuracy than the self reading ones, as by means
of the vernier the rod may be read to 1-1000 of a foot.
To measure the distance between two certain points, the rod is placed at one of
them, and the instrument over the other one; focus the rod precisely without paral-
lax, and then take the reading, that is, see how many feet, and fractions of a foot, are
1 by the two stadia wires in the held of view; add to the value of this reading
the focal length, plus the distance of object glass to the center of the axis, and the
sum is the desired distance between the two points.
The focal length of the object glass may be measured near enough for practical
purposes with any ordinary foot-rule, by focusiug a distant object, and then measur-
ing the distance from the object glass to the center of the capstan head screws, by
which the wires are adjusted, also, the distance from the object glass to the center
of the axis.
The sum of these measurements is a constant to be added to every slru/le stadia
reading, no matter how short or how long the distance may be. To enable the rod to
be held right angular to the line of sight on rising ground, a rodlevel should be used.
To a transit instrument intended to be used with the stadia, a vertical circle or arc
Bhonld be attached for measuring the augle of elevation or depression of the line of
sight on inclined ground, in order to reduce the stadia distance to the desired hori-
zontal distance.
The following will illustrate the necessity of employing first-class telescopes for
stadia measurements.
Innumerable experiments, made by various philosophers, have shown that the
human eye cannot perceive an object distinctly, when the angle which it subtends to
the eye is less than forty seconds, or when the eye views them from a distance equal
to 5,156 times their width.
This rale will change considerably with some individuals; while some are able
to see objects distinctly when the above angle is only thirty seconds, there are also
some with whom the above angle must not be less than sixty seconds. This pecu-
liarity of the human eye, limiting the angle of sight for distinct vision is independent
from long or short-sightedness.
This rule will also change with different degrees of illumination; it is, however,
based on the illumination afforded by fair daylight.
It is understood that it is immaterial whether a real object, or the image of an
object (as produced in a telescope), subtends the angle to the eye; both circum-
stances are subject to the same rules.
When a rod, divided to 1-100 of a foot, and having these divisions painted, alter-
nately, black and white, is viewed with a good telescope magnifying the diameter
twenty-eight times, the angle which is subtended to the eye by one such division of
the image, is equal to forty seconds, when the rod is 1,444 feet distant.
Under very favorable circumstances, when the rod is well illuminated, and the
atmosphere clear and pure, each character on the face of the rod may be seen clearly
and distinctly enough to permit direct stadia readings without the use of targets; but
28 CATALOGUE AND PRICE LIST OF
under most circumstances this distance from distinct view will be found, by reason
of the absorption of light, to be reduced to about 1,200 to 1,300 feet.
For greater distances, this rod will be found insufficient for correct stadia read-
ings, and either another rod with fewer divisions must be used, or the ordinary level-
ing rod provided with two targets.
With the aid of the above rule, knowing the magnifying power of the telescope,
and the longest probable sight which may be taken, a self-reading rod can always
be made to suit, if, for very long distances, allowance is always made for the
loss of light.
It -will thus be found, that the better the telescope, the finer may be the single
divisions on the self-reading rod, and, consequently, the stadia readings obtained will
be so much the closer.
One of the chances for errors in taking long stadia readings, is in the thickness of
the wires covering a portion of the greatly diminished image, and thus causing an un-
certainty in the readings, from center to center, of the wires. Considering that the
image of an object 1,500 feet distant, formed by a nine inch focal length object glass,
1
is diminished 2,000 times, 1-100 part of a foot in the object will only measure
200,000
1
part of a foot, or part of an inch in the image, which is far less than the very
1666
finest thread of a spider's web will cover. It will be found that closer stadia readings
may be obtained from upper to upper edge, or from lower to lower edge, of the
stadia wires. In the one case the intersected parts of the image are covered, while,
in the other one, the intersecting edges of the wires maybe considered mathematical
lines, not covering any space at all.
Both wires must, necessarily, be of the same thickness.
GLASS DIAPHRAGMS.
Quite a number of these have been cut by us for the U. S. Coast and Geodetic
Survey. A small disc of very thin glass is fasteued to the diaphragm instead of the
spider webs, and fine lines are drawn with a diamond on same; it is easily seen that
these cannot get out of shape; for stadia measurements we think them to be of great
advantage. The only disadvantage there may befound, is that small particles of dust
will settle on the plate glass sometimes, and as these are in the focus of the eye piece
they will always be visible to the observer.
We make no extra charge for putting these diaphragms into our new instruments
if ordered in time.
TABLE OF REFRACTIONS IN DECLINATION FOR SOLAR COMPASSES AND SOLAR TRANSITS.
(Vkom tt« Stmvsvoa'B Oowjuooh, published bj WM ft ntou, 1882.)
Bus:
BY BUB'S HF.CI.1N U'loNS NORTH,
From Hatch 9M to Beptembex 99d, us :
Pot
LailtO.de.
Hours
Irom
Merid.
Kir's ikflhiBllfll* in fantinil llm.
+ 203
(• 100
—
/ /.
/ // / //
/ //
May.
30O
1.
2.
:t.
4.
111
14
90
32
15
19
26
39
21
25
99
41;
27
31
69
June.
350
1.
2.
8.
4.
16
211
26
39
21
25
33
47
27
32
39
56
33
39
17
1 00
July.
400
1.
.j
:\.
4.
91
26
S3
47
27
32
41)
55
S3
39
48
1 05
111
40
1 18
August.
160
1.
2.
3.
4.
27
39
111
64
33
99
47
1 02
40
40
56
1 14
48
52
1 06
1 32
September.
600
1.
i
33
38
47
1 IM
40
46
66
1 45
48
56
1 on
2 00
57
1 06
1 20
3 00
-22d-
BY
SUN'S DECLINATIONS SOUTH,
Minus:
October.
From September 22d to March 22d, subtract :
For
Latitude.
Hours
from
Merid.
Sun's Declinations in Rauticnl Aim.
— 50
— 10O
— 160
— 203
/ //
/ //
* //
/ ti
November.
303
1.
2.
3.
4.
40
46
55
1 19
48
54
1 or,
1 35
66
1 10
1 18
1 57
i oo
1 is
1 36
2 29
December.
350
1.
4.
48
55
1 Oil
1 40
57
1 04
1 20
2 00
1 06
1 18
1 40
2 30
1 20
1 31
2 00
3 30
January.
400
1.
a.
4.
1 00
1 IIS
1 20
2 00
1 08
1 20
1 40
a so
1 30
1 36
2 00
3 20
1 40
2 00
2 40
5 00
February.
460
1.
2.
3.
4.
1 08
1 20
1 40
2 20
1 30
1 40
2 00
3 00
1 40
2 00
2 36
4 40
2 00
2 SO
Ll 30
8 00
March.
-22d—
500
1.
2.
3.
4.
I 30
1 36
2 30
3 00
1 40
2 00
2 45
4 30
2 00
2 30
3 30
7 00
2 40
3 15
5 00
15 00
TABLE OF THE CURVATURE
OF THE
EARTH.
Hist, in
miles.
Height.
Diet, in
miles.
Height.
It. in.
Dist. in
miles.
Height.
Dist. in
miles.
Height.
inches.
feet.
feet.
\
a
7
32 5
15
1411
40
10IU
H
■i
8
42.5
16
170
45
1346
1
8
8
51). s
17
192
60
1669
ft. in.
10
66.4
18
215
60
2394
2
2.6
11
80.2
111
240
70
3258
3
6
12
95.4
20
266
80
4255
4
10.6
18
112
26
415
90
5386
5
10.6
14
130
30
599
100
6649
6
23.9
35
814
PAET IT.
Catalogue and Price List
OF
IMPROVED
ENGINEERS'* SURVEYORS' INSTRUMENTS
"WARRANTED FIRST-CLASS.
MADE BY
-^_ X-.XET'Z Sz, CO-
(Successors to Karl Rahsskopff, )
No. 422 SACRAMENTO STREET,
SAN FRANCISCO.
32 CATALOGUE AND PRICE LIST OP
Engineers' and Surveyors' Transits.
Transits 9To. I to No. I C.
DIMENSIONS.
Horizontal Circle 6 J inches Diameter.
Vertical Arc 5 " "
Compass 4£ " "
ObjeetGlass 13-16
Weight of Instrument 15 J pounds.
Box 8
Tripod 8 "
The instrument is designed for engineering -work of a high class,
such as is required on bridge building, water works, and for city and
land surveying. The size of the circle is such that it may be gradu-
ated to read to 30" or 20" without fatigue to the eye. The Telescope
is of the best definition, and has a large aperture with perfectly flat
field. The eyepiece is achromatic, and gives a large field with plenty
of light. The horizontal circle has two double verniers, reading to
single minutes, which are placed so as to allow a reading without
stepping aside when sighting through the Telescope. Long compound
centers; improved Telescope object erect. Telescope balanced and
reversing both at eye and object ends, and with one end of its axis
adjustable; protection to object slide; shifting tripod head, and our
new improved tripod coupling. The case has a leather strap, hooks,
etc. It contains a sunshade, a plumb-bob, a magnifying glass, and
several adjusting pins.
Extras to Transit No. I to I C, Inclusive.
Striding Level to Axis of Telescope $20 00
Graduations on Horizontal Circle, on solid silver 10 00
reading to 30" 10 00
" " " " " 20" 20 00
" on Vertical Are or Vertical Circle, on solid silver.. 5 00
Gradientor Attachment 5 00
Stadia Wires, fixed 3 00
adjustable 10 00
Three Leveling Screws, instead of four. . 10 00
Shifting Center for Instrument with three leveling screws 5 00
Arrangement for Offsetting at Bight Angles 5 00
Variation Plate 10 00
Bottle of Watch Oil to lubricate the Centers 25
A. LIETZ * 00.
33
No. I.
As made by A.. LIETZ & CO.
PJLAIST TRAKTSIT.
Price as above S 185 00
For size and description of this Instrument, as well as for extras,
see preceding page.
34
CATALOGUE AND PRICE LIST OF
No. la
As made by A. LIETZ & CO.
TRANSIT, with Iievel Attachment to Telescope.
Price, as above, §215 00.
For size and particulars of this Instrument, as well as for extras,
see page 32.
A. LIITZ ft CO.
35
No. lb.
As made by A. LIETZ & CO.
Complete Engineers' and Surveyors' Transit.
Price, as above, $230 00.
For size and particulars of this Instrument, as well as for
Extras, see page 32.
36
CATALOGUE AND PRICE LIST OF
No. Ic.
As made by A. LIETZ & CO.
Complete Engineers' and Surveyors' Transit.
». i.n. i.
37
The sectional out, Fig. C, shows the construction, and the atten-
tion ol thi re is called to this point, on which steadiness and
Bfarength <>f the instrument principally depends. As will be observed,
the renters extend down to the base of the instrument, which oon«
struction permits giving them their full length, and at the same time
brings the plates or center of gravity as near as possible to the tripod
Fig. C.
SECTIONAL CUT
ENGINEERS' AND SURVEYORS' TRANSIT.
One improvement which we have added to all our instruments,
is this: We place an extra piece on the shoulder of the center (not
shown in the cut) on which the clamp fits. This extra piece enables us
to continue the outer center through the clamp up to the plates in the
Transits. It also serves to lessen the damage in case of a fall.
38
CATALOGUE AND PRICE LIST OF
No. 2.
As made by A. LIETZ & CO.
COMPLETE JlorXTlI\ ANT* JIIXIXG
TRANSIT.
A. LIETZ A :i!l
SMALL MOUNTAIN AND MINING TRANSIT,
So. 3. PLAIN TRANSIT.
This Instrument is made exactly us tlmsc enumerated under No. I,
with the exception of size aud weight. ~\Xe can recommend it as being
a very reliable and superior instrument for general land surveying and
mining purposes.
DIMENSIONS.
Horizontal Circle 5-inch diameter.
Vertical Arc 4 " "
Compass 3J " "
Object Glass 1 "
Weight of Instrument. ... 8i pounds.
Tripod 6J-7" "
Price as above $180 00
Extras to Plain Transit.
Vertical Circle (reading to minutes of Arc) $ 25 00
Or Vertical Arc 15 00
Clamp and Tangent Movement to Axis of Telescope 15 00
Long Level on Telescope, ground Graduated Bubble 15 00
Gradriation of Horizontal Circle, on solid silver 10 00
Vertical Circle, or Vertical Arc, on solid silver 5 00
Variation Plate 10 00
Arrangement for Offsetting at Right Angles 5 00
Three Leveling Screws, instead of four ; . . . 10 00
Shifting Center for Instrument with three leveling screws 5 00
Stadia Wires, fixed 3 00
" adjustable 10 00
Striding Level 20 00
Lamp for mining engineering, of brass, with ground leus 7 00
Reflector, for illuminating the cross-wires 4 00
Prism, attachable to eye-piece 8 00
Detachable side Telescope 35 00
Half-length Tripod 13 00
Extra Extension Tripod 15 00
Plummet Lamp 10 00
GradieDter Attachment 5 00
Large Plumb-bob, weight 4 pounds, for use in shafts ... 5 00
Bottle of fine watch oil 25
No. 3. MIMINQ TRANSIT Dimensions as in No. 1.
Graduations on solid silver; verniers, reading to minutes, are provided
with glass shades; 5-inch full vertical circle; spirit-level, clamp and
tangent screw to telescope; extension tripod, etc. Price, $253.
No. 4. miNINO TRANSIT.— Dimensions as in No. 2.
Graduations on solid silver; verniers, reading to minutes, are provided
with glass shades; 4-inch full vertical circle; spirit-level, clamp and
tangent screw to telescope; extension tripod, etc. Price, $253.
Mining Transits Constructed with Eccentric Telescopes to Order.
4(5 CATALOGUE AND PRICE LIST OF
TRANSIT-THEODOLITE.
For Use In Cities, in Tunnels, and for Triangulation.
No. 5. Of late years it has been found desirable to design a
transit for use -where instruments of ordinary construction would fail to
give satisfaction, or do not permit of rapid work where the highest
degree of accuracy is required. The instrument, as shown in the
accompanying illustration has no compass, and therefore the upper
frame mounting the telescope is in one piece, which is provided with
ribs, and which rests directly on the top flange of the inner center.
The result of this is that great lateral strength is obtained, which per-
mits of mounting the telescope axis by means of cylinders at each end
in wyes. On top of each bearing of the telescope axis is mounted a
cap provided with an adjusting screw, with which the necessary fric-
tion for the revolving telescope is obtained, and these caps are also
provided with two milled-headed screws, which can be removed readily
when the telescope is to be reversed for straight line measurements
over the bearings. These caps are so arranged as to completely exclude
dust from the axis. In this new arrangement the telescope can be
reversed as in ordinary instruments through the standards, as well as
over the bearings, as is usual in triangulation and for aligning straight
lines; and last, but not least, the movement of the telescope in the
vertical plane is the most accurate known. Ordinary transits cannot
fulfill these functions owing to the peculiar form of the bearings
wherein the telescope axis revolves, which bearings are so made to give
lateral stiffness to the telescope, on account of the slenderness of the
standards resting on the upper plate. The instrument is provided with
three or four leveling screws. The verniers can be placed at right
angles to the line of sight, or as shown in the cut. The dimensions,
etc, are: Horizontal plate 6J inches, graduation on solid silver pro-
tected as in our regular engineers' instrument; two double opposite
verniers, reading to 30"; two rows of figures in opposite directions;
long compound centers; 11-inch telescope (inverting or erect); 1J
inches clear aperture; power, 24 diameter; protection to object slide;
single spring tangent screws for the upper and lower plates; 4 leveling
screws; shifting center; split-leg tripod; case; etc.
Price for plain Transit- Theodolite $240.
Extras to Plain Transit-Theodolite.
FOE EXTRAS TO TUNNEl TRANSITS, SEE EXTRAS TO J1ISJSG TRANSITS, Page 3d.
Horizontal Limb 6% inches in diameter, verniers reading to 20" $ 10 00
" 7 " •' •' " 10" 35 00
Vertical Arc 5 " " " " minutes 20 00
Full 5-inch Vertical Circle, " " " 25 00
Two Reading Glasses, with ground glass shades to verniers 15 00
Instrument provided with 3 Leveling Screws 10 00
Shifting Center for Instrument with three leveling screws 5 00
Stadia Wires, fixed 3 00
adjustable 10 00
Striding Level 20 00
Six-inch Spirit Level with reversible clamp, tangent & gradienter to telescope 40 00
Oblong Compass, with motion for setting off the variation. (Three-inch
needle reads only a few degrees each way from zero. ) 20 00
Note.— A Plain Translt.Theodolite is without a level, clamp and arc to telescope.
A. L1E1Z .<. CO.
41
COMPLETE TBANSIT-THEODOLITE.
FOR USE
IN CITIES, IN TUNNELS, AND FOR TRI ANGULATION.
As made by A. LIETZ & CO.
4:2 CATALOGUE AND PEIOE LIST OF
THE LEVEL.
The three main qualities to be secured in a Level are: stability, powerful Tele-
scope and a sensitive Bubble.
In regard to the first point, an examination of the cut -will be sufficient to show
that this has been accomplished in a perfect manner. Our Patent Coupling, which
principally rendered this possible, as the instrument need not be taken apart in order
to attach it conveuiently and safely to the Tripod, aud the continuation of the center
through the clamp up to the bar, enabled us to bring the center of gravity as near as
possible to the Tripod Head.
The Center or Spindle is almost three and one-half inches long. Great care is
taken in fitting it to the socket, and, being made of steel, it will be apparent that it
is an utter impossibility to wear out these parts even by fifty years' constant use.
The liability of bending the Spindle, so common an accident with instruments having
brass centers, and the fretting of the same which will also sometimes happen, is alto-
gether avoided by a steel center. The fact is, that every level ought to have one, and
the reason for its omission by other makers is simply because it is more expensive
to manufacture.
It is always desirable to have a sensitive Bubble in Level, as the engineer will
sometimes be called upon to do accurate work, which a dull one is not capable of
performing. Our Level Tube is curved so as to give for every two minutes of angle
one inch motion of the Bubble. One inch of the scale is divided into twelve parts,
which gives for each division an angle of ten seconds, and as a moving of the Bubble
of one division will cause a difference of two in the reading of the two ends, it will
be seen that a difference of one division in the reading of the two ends indicate an
angle of five seconds.*
The remark is hardly necessary that a Level Telescope should have power and
definition. To obtain this result, and the same time to keep the dimensions of the
Telescope and the other parts of the instrument within the proper limits for steadi-
ness and portability, has been our earnest endeavor.
A length of 18 inches we have found the most advantageous in result . Expe-
rience has shown us that, though an increased length adds to the magnifying
power, it will only be of some value if the other parts of the instrument are enlarged
in proportion, which however, will make it too heavy for carrying conveniently.
While for some exceptional cases such an instrument might be preferable, we believe
that in our 18-inch Level we can meet even the most extensive requirements called
for in engineering.
Our new improved Eye Piece, and the application of a large diameter of object
glass and tubes than is usually found, enables us to obtain a magnifying power of 33.
The increase in size of diameter of object glass and tube adds but very little to the
weight of the Telescope, and does not require a longer bar and larger plates, as an
increase of length necessarily will, to retain steadiness. An aperture of one and
three-eighth inches used to its full value, as the tubes are large enough to let all the
rays proceeding from the object glass pass through to the field of view (which im-
portant point is disregarded in the majority of instruments of other makers), affords
a high illumination, with the above mentioned power. This power is in proportion
with the laws of optics given in our account of telescopes. t
It has been there shown that the size of the aperture of the object glass divided
by the power gives the diameter of the pencil of light entering the eye, and as this
in our Telescope is one and three-eighths, divided by thirty-three, giving one-twenty-
fourth of an inch, it will be seen that power and brightness are in accordance with
these laws. To force the power beyond these limits we cannot conscientiously do, as
it would be preferable only under certain circumstances, such as in a perfectly clear
atmosphere with a strong illumination of object.
The collars are made of the hardest bell metal, and of exactly equal diameter.
How important this equality is, will be seen in our account of Level Telescopes.
* Such a Bubble, however, will ouly do good service with an instrument perfectly steady and
provided with a powerful and sharply-defining Telescope. If placed in an instrument which in
construction is top heavy, or where the settling of the dust on the socket aud cone will throw out
the Y's every time they are detached from the leveling screws, it will only be a source of annoy-
ance in working. These defects are probably the cause why a great many engineers are prejudiced
against sensitive levels, and prefer a sluggish or dull one. "We assure the reader that a sensitive
bubble, even if a little out of center by reversing the instrument, will still afford better results than
a dull one, which gives the instrument the appearance of steadiness. The engineer only deceives
V. LIETZ A CO.
43
No. 6.
As made by A. LIETZ & CO.
18-INCH ENGINEERS' Y LEVEL.
Price, as shown, packed complete in bos, with usual accessories $145 00
For Agate Fitted Wye's, we make an additional charge of §10.00.
No. 7. ENGINEER'S DUMPY LEVEL.
This instrument — in Europe employed almost exclusively — has been used but
very little in American Engineering, caused partly by the greater inconvenience in
adjusting as compared with the Y Level, and partly on account of the defective con-
struction, inferior Telescope, etc., to be found in most of this style Instruments, we
believe that a Dumpy Level possessing a good Telescope, sensitive bubble and
stability, will do just as good work as tlie more costly Y Level, While the adjust-
ment of the latter is easier made, the former will retain it longer.
Our Dumpy Level has a steel centre, 15 inch Telescope, the Level is placed
between the Telescope and the bar, and the vial is curved so as to give for each inch
motion of the bubble an angle of 3 minutes. The instrument ie attached to the tri-
pod with our new tripod coupling.
The price is complete $100 00
The same with three leveling screws, $10 extra.
himself by using a poor Bubble giving apparent satisfaction by concealing thi errors which ft
sensitive one will show. A good instrument will not suiter from having its qualities indicated by a
sensitive Babble.
t To better understand the principles and laws of optics, by which the construction, power.
illumination, etc., of telescopes is governed, ihe reader would do well to study the short treatise
on telescopes we have inserted in this book. It will also serve to correct impressions formed by
some through several publications issued of late years, claiming what can only be called " sen-
sational qualities " for telescopes.
44
CATALOGUE AND PKIOE LIST OF
No. 8. PLANE TABLE.
The principal novelty in our Plane Table is the reduction of "weight effected by
the ribbing and bracing of all the heavy parts.
The table is usually 24 inches square, and consists of eight different pieces of
hard aud dry pine wood, which are so joined as to make warping impossible. The
Alidade is 21 inches, and the Telescope 15 inches long. The latter is either invert-
ing or erect, has a magnifying power of 32 diameters, and is always supplied with
stadia hairs.
The radius of the vertical arc, if such is attached, is 3% inches. In case a level
is required to the telescope, we recommend the " Striding Level." For the compass
a 4-inch needle will answer. The instrument is always provided with a plumbing bar.
The price of this instrument, with table 24 inches square, vertical circle or arc,
level to telescope, stadia hairs, compass box, clamp, etc., is $300.
SOLAR ATTACHMENTS-
No. 9. — G. N. Saeginuller's Patent Solar Attachment with sun shade and prism
for eye piece $60 00
No. 10. — Hchmolz Patent Solar Attachment with improved level for polar
axis adjustment $60 00
Advantages of the Solar Attachments.
The intelligent surveyor will readily understand that the more perfect horizon
obtained by the use of the telescope level, the greater length of the arcs allowing
finer readings of angles, and the use of a telescope in place of sights, all render the
solar attachment more accurate than the ordinary solar compass.
It can also be put on the telescope of any good traneit at comparatively small
cost, and thus enable the surveyor to establish the true meridian, to determine the
correct latitudes, and to obtain true time very nearly.
SURVEYOR'S COMPASS.
No. 11. The instrument has 5% inch needle, 14-inch plate, open sights, in
box with strap $45 00
No. 12. The same with Variation Plate 50 00
1 I ILT/. * CO.
45
No. 14.
Prismatic Compass, 3 inches diameter, with divided ring on needle arid fold-
ing sights: packed in neat case, very convenient for reconnoissance. . . .
$15 00
No. 15.
No. 15.
Small Pocket Compasses without and with sights, from.
.$lto?8 00
No. 16.
No. 16. Lock's Hand Level $8 75
No. 17. Lock's Hand Level, round 5 75
No. 18.
No. 18. Abney's Reflecting Level or Pocket Altimeter, improved, with
divided arc to show gradients, in morocco case, each $15 00
No. 19. Abney's Reflecting Level or Pocket Altimeter, with Bar Needle,
Compass and socket for Jacob Staff 18 00
46
CATALOGUE AND PBICE LIST OP
A NEW CLINOMETER.
Price $10 00.
"The accompanying exit is about half size and represents a new clinometer,
designee! by Melville Attwood for the use of the miner and prospector. It can easily
be carried in the pocket, aud is made as small as possible consistent with accuracy.
Attwood-s Clinometer, showing Compass.
E, is the graduated circle which is kept in place by a small spring at -4, a slight
pressure on the knob of which sets the circle free, and on the removal of the fingers
the instrument can be taken up and the angle of inclination easily read.
D represents a compass for taking approximate bearings.
£ and are small levels, one on the top and the other at the end of instrument.
Circle of Attwood's Clinometer.
With this Clinometer and a small straight-edge the under lay of any metaliferous
vein may be accurately taken, and in positions where a larger instrument could not
be used; also the dip of any bed, or stratum of rock or seam of coal. T\ _ '?
The timbering of any level, shaft or incline may be set by it. It can be used in
quartz mills to give the proper angle to the silvered plates, blanket, trays, and sluice
boxes. The instrument is a very practical one.
No. 21. Attwood's Improved Clinometer in metal frame $25 00
\. 1 1ET/ 1 47
Lump for Illuminating Graduations.
No. 22. Lamp for illuminating Kradnafioiis, cross wires, etc., for use in un-
derground work, of brass with ground lens
Small PIij miiiet Lamp of brass, steal point 8 IjO
No. M. Lars " " " 10 00
Plumb Hobs of the most improved shape, from ...$lto 5 00
'« i^_; ■ ■ -, » ^^^gag^^^B»
■Si
LEVELING RODS.
No. 26. Philadelphia self-reading rod with vernier clamp and target, read-
ing to lOOOths from G to 8 feet long $19-60- / 7f t?
JIIMVIi ROD.
No. 27. 3 feet long, sliding out to five feet with vernier clamps and target,
reading to wmiths $14 00
RANGING POLES.
No. 28. 6 and 8 feet long, with steel pointed shoe and divided red and white
alternately, each $2 75
No. 29. 7 feet long of steel, each 3 00
SURVEYOR'S CHAINS.
No. 30. Iron Chain, Brass Handles, No. 8 wire, 33 feet $ 2 60
" 31.
,. 32,
•' 33.
" 34. Steel Chains, " No. 10
..
"
" 38. Steel Chains brazed links and ring No. 12 wire,
39.
411.
41.
50 "
3 25
66 "
4 00
100 "
5 25
33 "
3 50
50 "
4 25
66 "
6 50
100 "
8 00
12 wire,
33 feet
50 "
5 50
6 00
f>
66 "
... . 10 00
"
100 "
11 50
€HESTER9IAN'S STEEL TAPES.
No. 42. 25 feet $ 4 50
•• 43. 33 " 5 50
"44. 50 " 7 50
'• 45. 66 " 10 00
" 46. 75 " 11 50
" 47.100 " 12 00
CHESTER MAN'S METALLIC TAPES.
No. 48. 33 feet $2 25
'• 40. 50 " 2 75
" 50. 66 " 3 00
" 51. 75 " 3 75
" 52.100 " 4 50
No. 53. Rod Level for Plumbing, a Rod or Flagstaff. . $5 OO
4:8 CATALOGUE AND PRICE LIST OF
STEEL WIRE OR RIBBON TAPES.
The general favor with which these tapes are received show that in the future
they will take the place of the heavy chains, with their hundreds of wearing places.
These tapes are intended for use wherever the chain can be used, and in many
places where it cannot. They are not intended to take the place of the light, finely
graded ones, but are especially designed for convenience and durability, and to take
the place of the chain in all land surveying, railroad and canal work and town platting.
"We use the best tempered " polished and blued" steel wire, 5-32 to 5-16 inch in
width, and Nos. 30 to 36 in thickness. For tapes 100 feet or under, we generally use
% inch, No. 32. Wider ribbon is more apt to get " kinked " and broken, and is
more affected by the wind. The graduations are- made on a surface of fine Babbit
Metal, of sufficient thickness to receive and retain the figures, which are of a size
corresponding to the width of the tape.
The tape is not easily broken by fair usage, but should an accident of that kind
occur it is easily mended by brightening the surface near the ends, then clasping
them with a sleeve of thin brass or tin and letting a little solder flow in, being care-
ful of course to keep the ends butted together and keep it straight while cooling.
The handles are made to unship, that by drawing the tape through the brush it
is not liable to catch anywhere.
Ribbon tape 100 feet long, divided every 10 feet, end foot in lOths, and last
foot in lOOths .....' $S-50 OVfV
Fifty feet, same as above 1 75 tfrSL^
Q£ f ^ JUJu — - — /-£ 7*~ y
J 3 i/ i, /■• — " V—'AjS
SEXTAST.
No. 54. Sextant of gun metal, light but very strong, 7-inch radius, 120
degrees, graduated on silver to 10 minutes, vernier reading to 10 seconds,
2 astronomical telescopes magnifying 6 and 10 times, 1 terrestrial tele-
scope, object glass Y% inch, seven neutral glasses aud two reflecting
mirrors. Instrument complete in polished mahogany box, each $120 00
"We keep supplies for Sextants always on hand.
ARTIFICIAL. HORIZONS.
No. 56. Mercurial Horizon, iron trough, iron bottle with screw stopper and
funnel cap, glazed metal roof. All in polished mahogany box §27 50
No. 57. Eeflecting Horizon, black glass plane mounted in brass, with three
leveling screws and spirit level, in polished mahogany case, each 16 00
A. Lit 1!'
ANEROID AND ALTITUDE
BAROMETERS.
C'j MJ)
Prices from $12 to §60 according to size and altitude scale.
Aneroid barometers made expressly for us by the best makers, in German silver
or nickel plated eases, truly compensated for temperature, with or without thei
mometers, raugiug from 5, Out) feet to 20, (10U feet, size 1" 4 . 'J 1 , and 5 inches. Guar-
anteed correct, every one being subjected to a severe test before being sold.
HIJUIIUll, STANDARD MOUNTAIN AND SEA
BAROMETERS.
Prices from $20.00 to $100.00.
Supplies for these Barometers, as tubes, mercury packings, etc., we ba>.
stantly on hand.
HELIOTROPES.
No. 58. Gauss Heliotrope ! $150 00
No. 59. The Telescope body is an iron tube, in the middle is a wood screw
with joint for attaching the Instrument to atree, or post. Price in box. 30 no
No. 60. Heliotrope as made by us for the United States Coast and Geodetic
Survey with wooden base, mirrors 4x4-. $35 00
No. til. Same as before, but with mirror GxG 41 oil
No. (12. Same with mirror, SxH 48 50
Prices for larger sizes on application.
No. 63. Pocket Heliotrope, Steinheii's, a beautiful instrument that requires
no adjustment. In case 25 00*
Extras to Heliotrope No. GO to 62 inclusive.
Tangent Screws for vertical and horizontal movement 7 50
Outlining arrangement for Tangent Screws 5 00
50
CATALOGUE AND PRICE LIST OF A. LIETZ & CO.
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ODOMETERS.
No. 64. For measuring distances by wagon. It is enclosed in a brass
box. i\i inches diameter, famished with leather case and double straps
to fasten to the center of the wheel. It is the most correct Odometer
for practical use . Price $17 00
No. 65. McDonnell Adometers 5 00
PEDOMETERS.
Pedometers are pocket instruments for measuring the distance traversed in
walking, the number of miles being registered by a mechanism inclosed in a nickel-
plated watchcasing, and operated by the motion of the body.
66. Watch size, registering 20 miles and divided in % of mile Price, $ 5 00
67. The same with three faces arid hands, registering single steps. . .Price, 9 00
'I. Atdvoud's Micrometers for Measuring Quartz
Screens.
It is a very small vest-pocket instrument by which the diameters of the aper-
tures in different punched slot and wire screens can be measured with tolerable accu-
racy. Those mill superintendents who are particular in their work will find this
little instrument a very handy one for the purposes indicated.
No. 68. In Brass, reading to 100 ths $1 50
No. 69. "Nickel, " " 175
No. 70. "Brass, " 20pths 2 50
No. 71. " " " " 2 75
' e ^= Z - ~
Proportional Dividers, Steel Spring Dividers, Bow Pens, Pencils.
Hatching Pens, Lithographers' Dividers, Curved Pens, Railroad Pens, Etc.
Prices according to quality of goods.
LEVEL CONSTRUCTED FOR THE USE OF MILLWRIGHTS,
MACHINISTS AND CARPENTERS. The Iron Frame is twenty-eight
inches long; has two adjustable levels six and three inches long.
No. 72. With Common levels $15 00
No. 73. Same with grand Levels 20 00
INDEX.
.-*«! Clinometer
... 40
SO
i'.i
Htude ■
Mercurial
Oneroid 4'.i
B
n 6
Chains 47
rrlpod, new 3-4
48
■ ■ I rapes -17
10
meter ic
Compass, I'll'' fl
Suveyors* Pocket , 44-45
traction of Instruments, General 7
Wires 10,12
Dumpy Level 43
" Adjusting 24
Engineers 1 Chains 47-48
Engineers' Dumpy Level 43
Wye Level 43
Extension Tripod 39
Graduation of Circles. <;
:. nti-r Screw 7
Heliotropes 49
Hand Level, Locke's 45
Lamp, for Mining Engineering 47
eling Instrument, Engineers* Dumpy 43
" Engineers' Wye 43
Level, Locke's 45
Leveling Kods 47
Leveling Screws 5
.Magnetic' Needle C
Mining Transit :!;>
Mountain Transit :;;i
'bjecl Gins;, Slide I'rotecter 22
... 11
ritH S
Pedonn i'i ... si
Piano Table 44
Plumb Bobs 17
Plumnx 17
4I-4.S
45
Rnftroad Trauslt. . ... 82
Hanging Pules 47
29
■ ■ I ■ ■ rui leni 13
Shifting Tripod: .->
vttachnieut 44
■ L.'VelR 6
Stadia Linus 7-2*
40
ora' Chains 47
Surveyors' C pass 11
. Surveyors' Transit 83-89
Taugent Screws 7
Tapes, Steel and ffletallic 47-4fi
Theodolite 41
Telesetipew. Description of u
Telescopes, Optical Principles 14
Transit City 41
Engineers' and Surveyors'
Mining 3H
" Mountain 39
Railroad 32
Til lolitG , 41
Tunnel 41
Transits, Adjusting, Directions fur 9
Adjustments nf ;i
Trip."!, Extension :[;i
Half Length :i0
Coupling 3-4
Variation Plate 32-88
Wye Level i;i
" Adjusting Directions lor n
Glass Diaphragms Page 28
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